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WO1998059048A9 - Recepteur pour une toxine de bacillus thuringiensis - Google Patents

Recepteur pour une toxine de bacillus thuringiensis

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Publication number
WO1998059048A9
WO1998059048A9 PCT/US1998/011868 US9811868W WO9859048A9 WO 1998059048 A9 WO1998059048 A9 WO 1998059048A9 US 9811868 W US9811868 W US 9811868W WO 9859048 A9 WO9859048 A9 WO 9859048A9
Authority
WO
WIPO (PCT)
Prior art keywords
toxin
nucleic acid
protein
fragment
seq
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US1998/011868
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English (en)
Other versions
WO1998059048A1 (fr
Inventor
Lee A Bulla
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
University of Wyoming
Original Assignee
University of Wyoming
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by University of Wyoming filed Critical University of Wyoming
Priority to CA002292644A priority Critical patent/CA2292644A1/fr
Priority to EP98926445A priority patent/EP1005547A1/fr
Priority to AU78283/98A priority patent/AU743234B2/en
Priority to BR9810217-6A priority patent/BR9810217A/pt
Priority to NZ501874A priority patent/NZ501874A/en
Publication of WO1998059048A1 publication Critical patent/WO1998059048A1/fr
Publication of WO1998059048A9 publication Critical patent/WO1998059048A9/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K14/00—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
    • C07K14/435—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans
    • C07K14/43504—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans from invertebrates
    • C07K14/43563—Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from animals; from humans from invertebrates from insects

Definitions

  • the invention relates to receptors that bind toxins from Bacillus thuringiensis and thus to pesticides and pest resistance. More particularly, the invention concerns recombinantly produced receptors that bind BT toxin and to their use in assays for improved pesticides, as well as in mediation of cell and tissue destruction, dissociation, dispersion, cell-to-cell association, and changes in morphology.
  • BT Bacillus thuringiensis
  • the present invention is based, in part, on the isolation and characterization of a receptor that is bound by members of the BT-toxin family of insecticidal proteins, hereinafter the BT-R, protein.
  • the present invention is further based on the isolation and characterization of a nucleic acid molecule that encodes the BT-toxin receptor, hereinafter BT-R gene. Based on these observations, the present invention provides compositions and methods for use in identifying agents that bind to the BT-R, protein as a means for identifying insecticidal agent and for identifying other members of the BT-R, family of proteins.
  • Figure 1 show the nucleotide sequence and deduced amino acid sequence of cDNA encoding the BT-R, protein from M. sexta.
  • Figure 2 shows a comparison of amino acid sequences of cadherin motifs (BTRcad-1 to 11) in BT-R, to those of other cadherins.
  • Figure 3 shows a block diagram of the cadherin-like structure of BT-R,.
  • Figure 4 shows the clone characterization of the BamHI-SacI fragment of BT-R,.
  • LM is Hindlll cut Lambda marker
  • UP is the uncut plasmid clone
  • NP is Nsil cut plasmid
  • XP is Xhol cut plasmid
  • BSP is BamHI and SacI cut plasmid showing the cloned fragment from BT-R
  • RM is mRNA size marker
  • RT1 and RT2 are transcribed mRNAs from the cloned BT-R, fragment.
  • Figure 5 illustrates the detection of protein expression from the plasmid containing the Bam-Sac fragment of BT-R, using 35 S-methionine as a tag.
  • LCR is a luciferase control mRNA to show that the rabbit reticulocyte lysates are functional;
  • RRl and RR2 are expression products of the Bam-Sac fragment of BT-R, produced in rabbit reticulocytes from mRNA; LCT is a luciferase control plasmid to show that the transcription/translation kit is functional; and TTl and TT2 are expression products of the Bam-Sac fragment of BT-R, produced in a transcription/translation kit.
  • Figure 6 shows a radio-blot of the Bam-Sac fragment of BT-R, with
  • BBMV is the brush border membrane vesicles from the midgut of M. sexta containing the wild-type BT-R, receptor protein
  • RBK is a rabbit reticulocyte blank
  • RRl and RR2 are the expression products of the Bam-Sac fragment of BT-R, produced in rabbit reticulocytes from mRNA
  • TBK is a transcription/translation kit blank
  • TTl and TT2 are expression products of the Bam-
  • Sac fragment of BT-R produced in a transcription/translation kit.
  • the arrows point to two of the bands.
  • Figure 7 shows the presence of a BT-R, homologue in Pink Bollworm and European Corn Borer identified using toxin binding similar to that used to identify the original BT-R, clone.
  • Figure 8 shows the binding of CrylAb to fragments of the BT-R, protein.
  • the present invention is based, in part, on the isolation and characterization of a novel protein expressed in the midgut of Manduca sexta that binds to members of the BT-toxin family of proteins, hereinafter the BT-R, protein.
  • the present invention specifically provides purified BT-R,, the amino acid sequence of BT-R,, as well as nucleotide sequences that encode BT-R,.
  • the BT-R, protein and nucleic acid molecules can serve as targets in identifying insecticidal agents. dc-l 18781 II. Specific Embodiments A. BT-R, Protein
  • the present invention provides, in part, the amino acid sequences of a BT-toxin receptor that is expressed in the midgut of Maduca sexta.
  • the present invention provides the ability to isolate or produce a previously unknown protein by using known purification methods, the cloned nucleic acid molecules herein described or by synthesizing a protein having the amino acid sequence herein disclosed.
  • BT-R refers to a protein that has the amino acid sequence of BT-R, provided in Figure 1, as well as allelic variants of the BT-R, sequence, and conservative substitutions mutants of the BT-R, sequence that have BT-R, activity.
  • BT-R is comprised of a single subunit, has a molecular weight of 210 kD, and has the amino acid sequence provided in Figure 1.
  • a prediction of the structure of BT-R, is provided in Figure 3.
  • the BT-R, protein of the present invention includes the specifically identified and characterized variant herein described, as well as allelic variants, conservative substitution variants and homologues ( Figure 7) that can be isolated/generated and characterized without undue experimentation following the methods outlined below.
  • allelic variants conservative substitution variants and homologues
  • Figure 7 allelic variants, conservative substitution variants and homologues that can be isolated/generated and characterized without undue experimentation following the methods outlined below.
  • all BT-R, proteins will be collectively referred to as the BT-R, proteins, the BT-R, proteins of the present invention or BT-R,.
  • BT-R includes all naturally occurring allelic variants of the Manduca sexta BT-R, protein provided in Figure 1.
  • Naturally occurring allelic variants of Manduca sexta BT-R will share significant homo logy, at least 75 %, and generally at least 90%, to the BT-R, amino acid sequence provided in Seq. ID No:2.
  • Allelic variants, though possessing a slightly different amino acid sequence than Seq. ID No:2, will be expressed as a transmembrane protein in the digestive tract of an insect or other organism.
  • allelic variants of the BT-R, protein will contain conservative amino acid substitutions from the BT-R, sequence herein described or will contain a substitution of an amino acid from a corresponding position in a BT-R, homologue (a BT-R, protein isolated from an organism other than Manduca sexta).
  • a BT-R protein isolated from an organism other than Manduca sexta.
  • allelic variants will be proteins that share a high degree of homology with at least a small region of the amino acid sequence provided in Seq. ID No: , but may further contain a radical departure from the sequence, such as a non- conservative substitution, truncation, insertion or frame shift.
  • Such alleles are termed mutant alleles of BT-R, and represent proteins that typically do not perform the same biological functions as does the BT-R, variant of Seq. ID No:2.
  • the BT-R, proteins of the present invention are preferably in isolated form.
  • a protein is said to be isolated when physical, mechanical or chemical methods are employed to remove the BT-R, protein from cellular constituents that are normally associated with the protein.
  • a skilled artisan can readily employ standard purification methods to obtain an isolated BT-R, protein. The nature and degree of isolation will depend on the intended use.
  • fragments of BT-R are particularly useful in: generating domain specific antibodies; identifying agents that bind to toxin binding domain on BT-R, ; identifying toxin-binding structures; identifying cellular factors that bind to BT-R,; isolating homologues or other allelic forms of BT-R,; and studying the mode of action ofBT-toxins.
  • Fragments of the BT-R, proteins can be generated using standard peptide synthesis technology and the amino acid sequence of Manduca sexta BT-R, disclosed herein. Alternatively, as illustrated in Example 5, recombinant methods can be used to generate nucleic acid molecules that encode a fragment of the BT-R, protein. Fragments of the BT-R, protein subunits that contain particularly interesting structures can be identified using art-known methods such as by using an immunogenicity plot, Chou-Fasman plot, Garnier-Robson plot, Kyte-Doolittle plot, Eisenberg plot, Karplus-Schultz plot or Jameson- Wolf plot of the BT-R, protein.
  • Fragments containing such residues are particularly useful in generating domain specific anti-BT-R, antibodies or in identifying cellular factors that bind to BT-R,.
  • One particular fragment that is preferred for use in identifying insecticidal agents is a soluble fragment of BT-R, that can bind to a member of the BT family of toxins.
  • Example 5 a fragment of BT-R, that binds to a BT-toxin is disclosed.
  • members of the BT-R, family of proteins can be used for, but are not limited to: 1) a target to identify agents that bind to BT-R,, 2) a target or bait to identify and isolate binding partners and cellular factors that bind to BT-R,, 3) an assay target to identify BT-R, and other receptor-mediated activity, and 4) a marker of cells that express a member of the BT-R, family of proteins.
  • the present invention further provides antibodies that bind BT-R,.
  • the most preferred antibodies will selectively bind to BT-R, and will not bind (or will only bind weakly) to non-BT-R, proteins.
  • Anti- BT-R, antibodies that are especially contemplated include monoclonal and polyclonal antibodies as well as fragments containing the antigen binding domain and/or one or more complement determining regions (CDRs) of these antibodies.
  • Antibodies are generally prepared by immunizing a suitable mammalian host using a BT-R, protein (synthetic or isolated), or fragment, in isolated or immunoconjugated form (Harlow, Antibodies, Cold Spring Harbor Press, NY (1989)).
  • Regions of the BT-R, protein that show immunogenic structure can readily be identified using art-known methods. Other important regions and domains can readily be identified using protein analytical and comparative methods known in the art, such as Chou-Fasman, Garnier-Robson, Kyte-Doolittle, Eisenberg, Karplus-Schultz or Jameson- Wolf analysis. Fragments containing these residues are particularly suited in generating specific classes of anti-BT-R, antibodies. Particularly useful fragments include, but are not limited to, the BT-toxin binding domain of BT-R, identified in Example 5.
  • Methods for preparing a protein for use as an immunogen and for preparing immunogenic conjugates of a protein with a carrier such as BSA, KLH, or other carrier proteins are well known in the art.
  • a carrier such as BSA, KLH, or other carrier proteins
  • direct conjugation with reagents such as carbodiimide may be used; in other instances linking reagents like those supplied by Pierce Chemical Co., Rockford, IL, may be effective.
  • BT-R BT-R
  • immunogen is conducted generally by injection over a suitable time period in combination with a suitable adjuvant, as is generally understood in the art.
  • titers of antibodies can be taken to determine adequacy of antibody formation.
  • the polyclonal antisera produced in this way may be satisfactory for some applications, for many other applications, monoclonal antibody preparations are preferred.
  • Immortalized cell lines which secrete a desired monoclonal antibody may be prepared using the standard method of Kohler and Milstein or modifications which effect immortalization of lymphocytes or spleen cells, as is generally known.
  • the immortalized cell lines secreting the desired antibodies are screened by immunoassay in which the antigen is the BT-R, protein or BT-R, fragment.
  • the cells can be cultured either in vitro or by production in ascites fluid.
  • the desired monoclonal antibodies are then recovered from the culture supernatant or from the ascites supernatant. Fragments of the monoclonals or the polyclonal antisera which contain the immunologically significant portion can be used as antagonists, as well as the intact antibodies. Use of immunologically reactive fragments, such as the Fab, Fab', of F(ab') 2 fragments is often preferable, especially in a therapeutic context, as these fragments are generally less immunogenic than the whole immunoglobulin.
  • the antibodies or fragments may also be produced, using current technology, by recombinant means. Regions that bind specifically to the desired regions of the BT-R, protein can also be produced in the context of chimeric or CDR grafted antibodies of multiple species origin.
  • anti-BT-R, antibodies are useful as modulators of BT-R, activity, are useful in in vitro and in vivo antibody based assays methods for detecting BT-R, expression/activity, in generating toxin conjugates, for purifying homologues of Manduca sexta BT-R,, in generating anti-ideotypic antibodies that mimic the BT-R, protein and in identifying competitive inhibitors of BT-toxin/BT-R, interactions.
  • the present invention is based, in part, on isolating nucleic acid molecules from Manduca sexta that encode BT-R,. Accordingly, the present invention further provides nucleic acid molecules that encode the BT-R, protein, as herein defined, preferably in isolated form.
  • BT-R encoding nucleic acid molecules
  • BT-R j genes encoding nucleic acid molecules
  • Figure 1 The nucleotide sequence of the Manduca sexta nucleic acid molecule that encodes one allelic form of BT-R, is provided in Figure 1.
  • nucleic acid molecule is defined as an RNA or DNA molecule that encodes a peptide as defined above, or is complementary to a nucleic acid sequence encoding such peptides.
  • Particularly preferred nucleic acid molecules will have a nucleotide sequence identical to or complementary to the Manduca sexta DNA sequences herein disclosed.
  • genomic DNA, cDNAs, synthetically prepared DNAs, and antisense molecules as well as nucleic acids based on an alternative backbone or including alternative bases, whether derived from natural sources or synthesized.
  • a skilled artisan can readily obtain these classes of nucleic acid molecules using the herein described BT-R] sequences.
  • nucleic acid molecules are defined further as being novel and unobvious over any prior art nucleic acid molecules encoding non-BT-R, proteins.
  • the BT-R] sequences of the present invention specifically excludes previously identified nucleic acid molecules that share only partial homology to BT-R].
  • Such excluded sequences include identified members of the cadhedrin family of proteins.
  • a nucleic acid molecule is said to be "isolated" when the nucleic acid molecule is substantially separated from contaminant nucleic acid molecules that encode polypeptides other than BT-R,.
  • a skilled artisan can readily employ nucleic acid isolation procedures to obtain an isolated BT-R, encoding nucleic acid molecule.
  • the present invention further provides fragments of the BT-R, encoding nucleic acid molecules of the present invention.
  • a fragment of a BT-R, encoding nucleic acid molecule refers to a small portion of the entire BT-R] sequence.
  • the size of the fragment will be determined by its intended use. For example, if the fragment is chosen so as to encode the toxin binding domain of BT-R, identified in
  • the fragment will need to be large enough to encode the toxin binding domain of the BT-R, protein. If the fragment is to be used as a nucleic acid probe or PCR primer, then the fragment length is chosen so as to obtain a relatively small number of false positives during probing/priming. Fragments of the Manduca sexta BT-R] gene that are particularly useful as selective hybridization probes or PCR primers can be readily identified from the entire BT-R] sequence using art-known methods.
  • Another class of fragments of BT-R, encoding nucleic acid molecules are the expression control sequence found upstream and downstream from the BT-R, encoding region found in genomic clones of the BT-R] gene. Specifically, tissue and developmental specific expression control elements can be identified as being 5' to the
  • BT-R encoding region found in genomic clones of the BT-R] gene.
  • Such expression control sequence are useful in generating expression vectors for expressing genes in the digestive tract of a transgenic organism.
  • a skilled artisan can readily use the BT-R] cDNA sequence herein described to isolate and identify genomic BT-R] sequences and the expression control elements found in the
  • Fragments of the BT-R, encoding nucleic acid molecules of the present invention i.e., synthetic oligonucleotides
  • PCR polymerase chain reaction
  • Fragments of the BT-R, encoding nucleic acid molecules of the present invention can easily be synthesized by chemical techniques, for example, the phosphotriester method of Matteucci, et al., JAm Chem Soc (1981) 103:3185-3191, or using automated synthesis methods.
  • DNA segments can readily be prepared by well known methods, such as synthesis of a group of oligonucleotides that define various modular segments of the BT-R] gene, followed by ligation of oligonucleotides to build the complete modified BT-R] gene.
  • the BT-R, encoding nucleic acid molecules of the present invention may further be modified so as to contain a detectable label for diagnostic and probe purposes.
  • probes can be used to identify nucleic acid molecules encoding other allelic variants or homologues of the BT-R, proteins and as described below, such probes can be used to identify the presence of a BT-R, protein as a means for identifying cells that express a BT-R, protein.
  • a variety of such labels are known in the art and can readily be employed with the BT-R, encoding molecules herein described. Suitable labels include, but are not limited to, biotin, radiolabeled nucleotides, biotin, and the like. A skilled artisan can employ any of the art-known labels to obtain a labeled BT-R, encoding nucleic acid molecule.
  • BT-R protein from Manduca sexta and the corresponding encoding nucleic acid molecules
  • a skilled artisan can readily use the amino acid sequence of the Manduca sexta BT-R, protein to generate antibody probes to screen expression libraries prepared from cells and organisms.
  • polyclonal antiserum from mammals such as rabbits immunized with the purified protein (as described above) or monoclonal antibodies can be used to probe an expression library, prepared from a target organism, to obtain the appropriate coding sequence for a BT-R, homologue.
  • the cloned cDNA sequence can be expressed as a fusion protein, expressed directly using its own control sequences, or expressed by constructing an expression cassette using control sequences appropriate to the particular host used for expression of the enzyme.
  • a portion of the BT-R, encoding sequence herein described can be synthesized and used as a probe to retrieve DNA encoding a member of the BT-R, family of proteins from organisms other than Manduca sexta, allelic variants of the Manduca sexta BT-R, protein herein described, and genomic sequence containing the BT-R] gene. Oligomers containing approximately 18-20 nucleotides (encoding about a
  • 6-7 amino acid stretch are prepared and used to screen genomic DNA or cDNA libraries to obtain hybridization under stringent conditions or conditions of sufficient stringency to eliminate an undue level of false positives.
  • pairs of oligonucleotide primers can be prepared for use in a polymerase chain reaction (PCR) to selectively amplify/clone a BT-R, -encoding nucleic acid molecule, or fragment thereof.
  • PCR polymerase chain reaction
  • a PCR denature/anneal/extend cycle for using such PCR primers is well known in the art and can readily be adapted for use in isolating other BT-R, encoding nucleic acid molecules.
  • Regions of the Manduca sexta BT-R] gene that are particularly well suited for use as a probe or as primers can be readily identified by one skilled in the art.
  • Non-Manduca sexta homologues of BT-R naturally occurring allelic variants of the Manduca sexta BT-R] gene and genomic BT-R] sequences will share a high degree of homo logy to the Manduca sexta BT-R] sequence herein described.
  • nucleic acid molecules will hybridize to the Manduca sexta BT-R] sequence under high stringency.
  • sequences will typically contain at least 70% homology, preferably at least 80%, most preferably at least 90% homology to the Manduca sexta BT-R] sequence of Seq. ID No:l.
  • nucleic acid molecules that encode homologues of the Manduca sexta BT-R, protein will hybridize to the Manduca sexta BT-R] sequence under stringent conditions.
  • Stringent conditions are those that (1) employ low ionic strength and high temperature for washing, for example, 0.015M NaCl/0.0015M sodium titrate/0.1% SDS at 50°C, or (2) employ during hybridization a denaturing agent such as formamide, for example, 50% (vol/vol) formamide with 0.1% bovine serum albumin/0.1% Ficoll/0.1% polyvinylpyrrolidone/50 mM sodium phosphate buffer at pH 6.5 with 750 mM NaCl, 75 mM sodium citrate at 42°C.
  • formamide for example, 50% (vol/vol) formamide with 0.1% bovine serum albumin/0.1% Ficoll/0.1% polyvinylpyrrolidone/50 mM sodium phosphate buffer at pH 6.5 with 750 mM NaCl, 75
  • Another example is use of 50% formamide, 5 x SSC (0.75M NaCl, 0.075 M sodium citrate), 50 mM sodium phosphate (pH 6.8), 0.1% sodium pyrophosphate, 5 x Denhardt's solution, sonicated salmon sperm DNA (50 ⁇ g/ml), 0.1% SDS, and 10% dextran sulfate at 42°C, with washes at 42°C. in 0.2 x SSC and 0.1% SDS.
  • a skilled artisan can readily determine and vary the stringency conditions appropriately to obtain a clear and detectable hybridization signal.
  • the present invention further provides recombinant DNA molecules (rDNAs) that contain a BT-R, encoding sequences as herein described, or a fragment thereof, such as a soluble fragment of BT-R, that contains the BT-toxin binding site.
  • a rDNA molecule is a DNA molecule that has been subjected to molecular manipulation in vitro. Methods for generating rDNA molecules are well known in the art, for example, see Sambrook et al., Molecular Cloning (1989).
  • a BT-R encoding DNA sequence that encodes a
  • BT-R protein or a fragment of BT-R, is operably linked to one or more expression control sequences and/or vector sequences.
  • a vector contemplated by the present invention is at least capable of directing the replication or insertion into the host chromosome, and preferably also expression, of the BT-R, encoding sequence included in the rDNA molecule.
  • Expression control elements that are used for regulating the expression of an operably linked protein encoding sequence are known in the art and include, but are not limited to, inducible promoters, constitutive promoters, secretion signals, enhancers, transcription terminators and other regulatory elements.
  • an inducible promoter that is readily controlled, such as being responsive to a nutrient in the host cell's medium, is used.
  • secretion signals it may be desirable to use secretion signals to direct the secretion of the BT-R, protein, or fragment, out of the cell.
  • the vector containing a BT-R, encoding nucleic acid molecule will include a prokaryotic replicon, i.e., a DNA sequence having the ability to direct autonomous replication and maintenance of the recombinant DNA molecule intrachromosomally in a prokaryotic host cell, such as a bacterial host cell, transformed therewith.
  • a prokaryotic replicon i.e., a DNA sequence having the ability to direct autonomous replication and maintenance of the recombinant DNA molecule intrachromosomally in a prokaryotic host cell, such as a bacterial host cell, transformed therewith.
  • a prokaryotic host cell such as a bacterial host cell, transformed therewith.
  • vectors that include a prokaryotic replicon may also include a gene whose expression confers a detectable marker such as a drug resistance.
  • Typical bacterial drug resistance genes are those that confer resistance to ampicillin or tetracycline.
  • Vectors that include a prokaryotic replicon can further include a prokaryotic or viral promoter capable of directing the expression (transcription and translation) of the
  • BT-R encoding sequence in a bacterial host cell, such as E. coli.
  • a promoter is an expression control element formed by a DNA sequence that permits binding of RNA polymerase and transcription to occur.
  • Promoter sequences compatible with bacterial hosts are typically provided in plasmid vectors containing convenient restriction sites for insertion of a DNA segment of the present invention. Typical of such vector plasmids are pUC8, pUC9, pBR322 and pBR329 available from Biorad Laboratories (Richmond, CA), pPL and pKK223 available from Pharmacia, Piscataway, NJ.
  • Expression vectors compatible with eukaryotic cells can also be used to variant rDNA molecules that contain a BT-R, encoding sequence.
  • Eukaryotic cell expression vectors are well known in the art and are available from several commercial sources. Typically, such vectors are provided containing convenient restriction sites for insertion of the desired DNA segment. Typical of such vectors are PSVL and pKSV-10 (Pharmacia), pBPV- l/pML2d (International Biotechnologies, Inc.), pTDTl (ATCC, #31255), the vector pCDM8 described herein, and the like eukaryotic expression vectors.
  • Eukaryotic cell expression vectors used to construct the rDNA molecules of the present invention may further include a selectable marker that is effective in an eukaryotic cell, preferably a drug resistance selection marker.
  • a preferred drug resistance marker is the gene whose expression results in neomycin resistance, i.e., the neomycin phosphotransferase (neo) gene. Southern et al. , JMol Anal Genet ( 1982) 1 :327-341.
  • the selectable marker can be present on a separate plasmid, and the two vectors are introduced by cotransfection of the host cell, and selected by culturing in the presence of the appropriate drug for the selectable marker.
  • the present invention further provides host cells transformed with a nucleic acid molecule that encodes a BT-R, protein of the present invention, either the entire BT-R, protein or a fragment thereof.
  • the host cell can be either prokaryotic or eukaryotic.
  • Eukaryotic cells useful for expression of a BT-R, protein are not limited, so long as the cell line is compatible with cell culture methods and compatible with the propagation of the expression vector and expression of a BT-R] gene.
  • Preferred eukaryotic host cells include, but are not limited to, yeast, insect and mammalian cells, the most preferred being cells that do not naturally express a BT-R, protein. Any prokaryotic host can be used to express a BT-R,-encoding rDNA molecule.
  • the preferred prokaryotic host is E. coli.
  • Transformation of appropriate cell hosts with an rDNA molecule of the present invention is accomplished by well known methods that typically depend on the type of vector used and host system employed.
  • electroporation and salt treatment methods are typically employed, see, for example, Cohen et al, Proc Acad Sci USA (1972) 69:2110; and Maniatis et al, Molecular Cloning, A Laboratory Manual, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY (1982).
  • electroporation, cationic lipid or salt treatment methods are typically employed, see, for example, Graham et al, Virol (1913) 52:456; Wigler et al, Proc Natl
  • Successfully transformed cells i.e., cells that contain an rDNA molecule of the present invention
  • cells resulting from the introduction of an rDNA of the present invention can be cloned to produce single colonies. Cells from those colonies can be harvested, lysed and their DNA content examined for the presence of the rDNA using a method such as that described by Southern, JMolBiol (1975) 98:503, or Berent et al, Biotech (1985) 3:208 or the proteins produced from the cell assayed via an immunological method.
  • the present invention further provides methods for producing a BT-R, protein that uses one of the BT-R, encoding nucleic acid molecules herein described.
  • the production of a recombinant BT-R, protein typically involves the following steps. First, a nucleic acid molecule is obtained that encodes a BT-R, protein or a fragment thereof, such as the nucleic acid molecule depicted in Figure 1.
  • the BT-R, encoding nucleic acid molecule is then preferably placed in an operable linkage with suitable control sequences, as described above, to generate an expression unit containing the BT-R, encoding sequence.
  • the expression unit is used to transform a suitable host and the transformed host is cultured under conditions that allow the production of the
  • the BT-R, protein is isolated from the medium or from the cells; recovery and purification of the protein may not be necessary in some instances where some impurities may be tolerated.
  • the desired coding sequences may be obtained from genomic fragments and used directly in an appropriate host.
  • the construction of expression vectors that are operable in a variety of hosts is accomplished using an appropriate combination of replicons and control sequences.
  • the control sequences, expression vectors, and transformation methods are dependent on the type of host cell used to express the gene and were discussed in detail earlier.
  • Suitable restriction sites can, if not normally available, be added to the ends of the coding sequence so as to provide an excisable gene to insert into these vectors.
  • a skilled artisan can readily adapt any host/expression system known in the art for use with BT-R, encoding sequences to produce a BT-R, protein.
  • agents and cellular constituents that bind to BT-R can be identified by: 1) the ability of the agent/constituent to bind to BT-R,, 2) the ability to block BT-toxin binding to BT-R, , and/or 3) the ability to kill BT-R, expressing cells.
  • Activity assays for BT-R, activity and binding and competitive assays using a BT-R, protein are suitable for use in high through-put screening methods, particularly using a soluble fragment of BT-R, that contains the BT-toxin binding domain, such as that disclosed in Example 5.
  • BT-R is mixed with an agent or cellular extract. After mixing under conditions that allow association of BT-R, with the agent or component of the extract, the mixture is analyzed to determine if the agent/component bound to the BT-R,. Binding agents/components are identified as being able to bind to BT-R, .
  • BT-R, activity can be directly assessed as a means for identifying agonists and antagonists of BT-R, activity.
  • targets that are bound by a BT-R, protein can be identified using a yeast two-hybrid system or using a binding-capture assay.
  • yeast two hybrid system an expression unit encoding a fusion protein made up of one subunit of a two subunit transcription factor and the BT-R, protein is introduced and expressed in a yeast cell.
  • the cell is further modified to contain 1) an expression unit encoding a detectable marker whose expression requires the two subunit transcription factor for expression and 2) an expression unit that encodes a fusion protein made up of the second subunit of the transcription factor and a cloned segment of DNA.
  • the expression results in the interaction of the BT-R, and the encoded protein. This brings the two subunits of the transcription factor into binding proximity, allowing reconstitution of the transcription factor. This results in the expression of the detectable marker.
  • the yeast two hybrid system is particularly useful in screening a library of cDNA encoding segments for cellular binding partners of BT-R, .
  • the BT-R, protein used in the above assays can be: an isolated and fully characterized protein, a fragment of a BT-R, protein (such as a soluble fragment containing the BT-toxin binding site), a cell that has been altered to express a BT-R, protein/fragment or a fraction of a cell that has been altered to express a BT-R, protein/fragment.
  • the BT-R, protein can be the entire BT-R, protein or a defined fragment of the BT-R, protein. It will be apparent to one of ordinary skill in the art that so long as the BT-R, protein or fragment can be assayed for agent binding, e.g., by a shift in molecular weight or activity, the present assay can be used.
  • the method used to identify whether an agent/cellular component binds to a BT-R, protein will be based primarily on the nature of the BT-R, protein used. For example, a gel retardation assay can be used to determine whether an agent binds to BT-R, or a fragment thereof. Alternatively, immunodetection and biochip technologies can be adopted for use with the BT-R, protein. A skilled artisan can readily employ numerous art-known techniques for determining whether a particular agent binds to a BT-R, protein.
  • Agents and cellular components can be further, or alternatively, tested for the ability to block the binding of a BT-toxin to a BT-R, protein/fragment.
  • antibodies to the BT-toxin binding site or other agents that bind to the BT-toxin binding site on the BT-R, protein can be used in place of the BT-toxin.
  • Agents and cellular components can be further tested for the ability to modulate the activity of a BT-R, protein using a cell-free assay system or a cellular assay system. As the activities of the BT-R, protein become more defined, functional assays based on the identified activity can be employed.
  • an agent is said to antagonize BT-R, activity when the agent reduces BT-R, activity.
  • the preferred antagonist will selectively antagonize BT-R,, not affecting any other cellular proteins. Further, the preferred antagonist will reduce BT-R, activity by more than 50%, more preferably by more than 90%, most preferably eliminating all BT-R, activity.
  • an agent is said to agonize BT-R, activity when the agent increases BT-R, activity.
  • the preferred agonist will selectively agonize BT-R,, not affecting any other cellular proteins.
  • the preferred antagonist will increase BT-R, activity by more than 50%, more preferably by more than 90%, most preferably more than doubling BT-R, activity.
  • Agents that are assayed in the above method can be randomly selected or rationally selected or designed.
  • an agent is said to be randomly selected when the agent is chosen randomly without considering the specific sequences of the BT-R, protein or BT-toxin.
  • An example of randomly selected agents is the use of a chemical library or a peptide combinatorial library, or a growth broth of an organism or plant extract.
  • an agent is said to be rationally selected or designed when the agent is chosen on a nonrandom basis that takes into account the sequence of the target site and/or its conformation in connection with the agent's action.
  • Agents can be rationally selected or rationally designed by utilizing the peptide sequences that make up the BT-R, protein and BT-toxin.
  • a rationally selected peptide agent can be a peptide whose amino acid sequence is identical to a fragment of a
  • BT-R protein or BT-toxin.
  • agents tested in the methods of the present invention can be, as examples, peptides, small molecules, and vitamin derivatives, as well as carbohydrates.
  • agents used in the present screening method are peptide agents whose amino acid sequences are chosen based on the amino acid sequence of the BT-R, protein or BT-toxin. Small peptide agents can serve as competitive inhibitors of BT-R, protein activity.
  • Peptide agents can be prepared using standard solid phase (or solution phase) peptide synthesis methods, as is known in the art.
  • the DNA encoding these peptides may be synthesized using commercially available oligonucleotide synthesis instrumentation and produced recombinantly using standard recombinant production systems. The production using solid phase peptide synthesis is necessitated if non-gene-encoded amino acids are to be included.
  • Another class of agents of the present invention are antibodies immunoreactive with critical positions of the BT-R, protein. As described above, antibodies are obtained by immunization of suitable mammalian subjects with peptides, containing as antigenic regions, those portions of the BT-R, protein intended to be targeted by the antibodies. Critical regions particularly include the BT-toxin binding domain identified in Example 5. Such agents can be used in competitive binding studies to identify second generation BT-R, binding agents.
  • the cellular extracts tested in the methods of the present invention can be, as examples, aqueous extracts of cells or tissues, organic extracts of cells or tissues or partially purified cellular fractions.
  • a skilled artisan can readily recognize that there is no limit as to the source of the cellular extract used in the screening method of the present invention.
  • the preferred source for isolating cellular binding partners of BT-R are cells that express BT-R, or cells that are in close proximity to BT-R, expressing cells.
  • An outline of one screening method is as follows. Cells are modified by transfection, retroviral infection, electroporation or other known means, to express a BT-R, protein and then cultured under conditions wherein the receptor protein is produced and displayed.
  • the cells are then recovered from the culture for use in the assay, or the culture itself can be used er se.
  • the modified cells are contacted with the candidate toxin and the effect on metabolism or morphology is noted in the presence and absence of the candidate.
  • the effect may be cytotoxic — i.e., the cells may themselves exhibit one of the indices of cell death, such as reduced thymidine uptake, slower increase in optical density of the culture, reduced exclusion of vital dyes (e.g., trypan blue), increased release of viability markers such as chromium and rubidium, and the like.
  • the differential response between the toxin-treated cells and the cells absent the toxin is then noted.
  • the strength of the toxin can be assessed by noting the strength of the response.
  • assays may be conducted directly as described above or competitively with known toxins. For example, one approach might be to measure the diminution in binding of labeled BT cry toxin in the presence and absence of the toxin candidate.
  • the screen can be used to devise improved forms of toxins which are more specific or less specific to particular classes of insects as desired.
  • the ability to determine binding affinity (K, and K j ), dissociation and association rates, and cytotoxic effects of a candidate allows quick, accurate and reproducible screening techniques for a large number of toxins and other ligands under identical conditions which was not possible heretofore. Such information will facilitate the selection of the most effective toxins and ligands for any given receptor obtained from any desired host cell.
  • Competition assays may also employ antibodies that are specifically immunoreactive with the receptor.
  • Such antibodies can be prepared in the conventional manner by administering the purified receptor to a vertebrate animal, monitoring antibody titers and recovering the antisera or the antibody-producing cells for immortalization, to obtain immortalized cells capable of secreting antibodies of the appropriate specificity.
  • Techniques for obtaining immortalized B cells and for screening them for secretion of the desired antibody are now conventional in the art.
  • the resulting monoclonal antibodies may be more effective than the polyclonal antisera as competition reagents;, furthermore, the availability of the immortalized cell line secreting the desired antibody assures uniformity of production of the same reagent over time.
  • Ligands include natural and modified toxins, antibodies (anti-receptor and antiidiotypic antibodies which mimic a portion of a toxin that binds to a receptor, and whatever small molecules bind the receptors.
  • BT-R is the target for the insecticidal activity of BT-toxins.
  • Agents that bind a BT-R, protein can be used: 1) to kill BT-R, expressing cells, 2) to identify agents that block the interaction of a BT-toxin with BT-R, and 3) in methods for identifying cells that express BT-R,.
  • binding agents will be based primarily on the nature of the BT-R, binding agent and its intended use.
  • a BT-R, binding agent can be used to: deliver a conjugated toxin to a BT-R, expressing cell; modulate BT-R, activity; directly kill BT-R, expressing cells; or screen for and identify competitive binding agents.
  • An agent that inhibits the activity of BT-R can be used to directly inhibit the growth of BT-R, expressing cells.
  • identified cellular factors that bind to BT-R can, themselves, be used in binding/competitive assays to identify agonist and antagonists of BT-R,.
  • the present invention further provides methods for identifying cells, tissues or organisms expressing a BT-R, protein or a BT-R] gene. Such methods can be used to diagnose the presence of cells or an organism that expresses a BT-R, protein in vivo or in vitro.
  • the methods of the present invention are particularly useful in the determining the presence of cells that are a target for BT-toxin activity or for identifying susceptibility of an organism to a BT-toxin or BT-toxin-like agent.
  • the presence of a BT-R, protein can be identified by determining whether a BT-R, protein, or nucleic acid encoding a BT-R, protein, is expressed in a cell, tissue or organism.
  • a variety of immunological and molecular genetic techniques can be used to determine if a BT-R, protein is expressed/produced in a particular cell or sample.
  • an extract containing nucleic acid molecules or an extract containing proteins is prepared. The extract is then assayed to determine whether a BT-R, protein, or a BT-R, encoding nucleic acid molecule, is produced in the cell.
  • a suitable nucleic acid sample is obtained and prepared using conventional techniques. DNA can be prepared, for example, simply by boiling a sample in SDS.
  • the extracted nucleic acid can then be subjected to amplification, for example by using the polymerase chain reaction (PCR) according to standard procedures, such as a RT-PCR method, to selectively amplify a BT-R, encoding nucleic acid molecule or fragment thereof.
  • PCR polymerase chain reaction
  • the size or presence of a specific amplified fragment is then determined using gel electrophoresis or the nucleotide sequence of the fragment is determined (for example, see Weber and May Am JHum Genet (1989) 44:388-339; Davies, J. et al. Nature (1994) 371 :130-136)).
  • the resulting size of the fragment or sequence is then compared to the known BT-R, proteins encoding sequences, for example via hybridization probe. Using this method, the presence of a BT-R, protein can be identified.
  • a suitable protein sample is obtained and prepared using conventional techniques.
  • Protein samples can be prepared, for example, simply by mixing a sample with SDS followed by salt precipitation of a protein fraction.
  • the extracted protein can then be analyzed to determine the presence of a BT-R, protein using known methods. For example, the presence of specific sized or charged variants of a protein can be identified using mobility in an electric filed. Alternatively, antibodies can be used for detection purposes.
  • a skilled artisan can readily adapt known protein analytical methods to determine if a sample contains a BT-R, protein.
  • BT-R, protein or gene expression can also be used in methods to identify agents that decrease the level of expression of a BT-R] gene.
  • cells or tissues expressing a BT-R, protein can be contacted with a test agent to determine the effects of the agent on BT-R, protein/gene expression.
  • Agents that activate BT-R, protein/gene expression can be used as an agonist of BT-R, activity whereas agents that decrease BT-R, protein/gene expression can be used as an antagonist of BT-R, activity.
  • the present invention further provides methods of sensitizing cells such that they become susceptible to killing with a BT-toxin, or a BT-toxin analog.
  • host cells transformed to express BT-R, receptor, or a homolog of the BT-R, receptor become sensitive to the mode of action of BT-toxins.
  • the binding of a BT-toxin to a BT-R, receptor expressed on the surface of the transformed cells results in induction of a cellular death and apoptosis of the cell expressing the BT-R, receptor.
  • the BT-R, receptor is an appropriate candidate for use in transforming cells in which it is desirable to induce cell death.
  • BT-R BT-R-encoding DNA molecules into a tumor cell
  • tumor cells within a patient can be engineered to express a BT-R, protein.
  • Such cells then become susceptible to death upon treatment with a BT-toxin. Since BT-toxin is not normally toxic to mammalian cells, this method is particularly applicable to inducing cell death in particular cells in a mammalian host.
  • Other situations where it may be desirable to stimulate cell death in particular cells or cell lines are in the treatment of autoimmune disorders and in the treatment of cells harboring pathogens, such as malaria or HIV agents.
  • the BT-R] gene and the BT-R, protein can also serve as a target for generating transgenic organisms in which the pattern of BT-R, expression has been altered.
  • BT-R, deficient insects or insect cells can be generated using standard knock-out procedures to inactivate a BT-R] gene, or, if such animals are non-viable, inducible BT-R] antisense molecules can be used to regulate BT-R] activity/expression.
  • cells or an organism can be altered so as to contain a Manduca sexta BT-R, encoding nucleic acid molecule or an antisense-BT-R, expression unit that directs the expression of a BT-R, protein or an antisense molecule in a tissue specific fashion.
  • an organism or cells for example insects or insect cells, is generated in which the expression of a BT-R] gene is altered by inactivation or activation and/or replaced by a Manduca sexta BT-R] gene. This can be accomplished using a variety of art-known procedures such as targeted recombination.
  • the BT-R] expression altered cells or organisms can be used to 1) identify biological and pathological processes mediated by the BT-R, protein, 2) identify proteins and other genes that interact with the BT-R, protein, 3) identify agents that can be exogenously supplied to overcome a BT-R, protein deficiency and 4) serve as an appropriate screen for identifying mutations within the
  • BT-R gene that increases or decreases activity.
  • transgenic insects such as members of the dipteran order, expressing the Manduca sexta minigene encoding BT-R, in a tissue specific-fashion and test the effect of over-expression of the protein in tissues and cells that normally do not contain the BT-R, protein.
  • the present invention further provides the expression control sequences found 5' of the of the newly identified BT-R] gene in a form that can be used in generating expression vectors.
  • the BT-R] expression control elements such as the
  • BT-R promoter
  • BT-R promoter
  • BT-R can readily be identified as being 5' from the ATG start codon in the BT-R] gene, can be used to direct the expression of an operably linked protein encoding DNA sequence. Since BT-R, expression is mostly tissue-specific, the expression control elements are particularly useful in directing the expression of an introduced transgene in a tissue specific fashion. A skilled artisan can readily use the BT-R, gene promoter and other regulatory elements to generate expression vectors using methods known in the art.
  • BT-R Protein Midguts of M. sexta were extracted and the BT-R, protein purified according to the method of Vadlamudi, R.K. et al. JBiol Chem (1993) 268:1233, referenced above and incorporated herein by reference.
  • the electroeluted band was confirmed to contain BT-R, protein by binding to us l-cryIAb toxin.
  • the protein bound to toxin had an apparent weight of approximately 210 kD under reducing and nonreducing conditions.
  • the purified electroeluted BT-R was subjected to cyanogen bromide digestion and the cyanogen bromide fragments separated on a 17% high-resolution tricine SDS- polyacrylamide gel as described by Schagger, H. et al. Anal Biochem (1987) 166:368.
  • the separated fragments were transferred to Problott membranes (Applied Biosystems) and five bands were extracted and subjected to microsequencing using standard instrumentation.
  • the amino acid sequences obtained were:
  • Synthetic oligonucleotides corresponding to peptides 1-3 of Example 1 were labeled with ⁇ 32 P using polynucleotide kinase and used as probes as described in the standard cloning manual of Maniatis, T. et al. Molecular Cloning: A Laboratory Manual (Cold Spring Harbor
  • a clone hybridizing to all three probes identified from 40 positive clones as hybridizing to all three of the probes was plaque-purified from a screen of 4 X 10 5 recombinants and subcloned into pBluescript (Stratagene). It contained an insert of 5571 bp. Double-stranded cDNA in pBluescript was sequenced in both directions by the dideoxy termination method with Sequanase (USB) according to the manufacturer's instructions. The sequencing showed an open reading frame of 4584 base pairs or 1528 amino acids along with a polyadenylation signal at position 5561. The sequence obtained and the deduced amino acid sequence is shown in Figure 1.
  • the deduced protein has a molecular mass of 172 kD and a pi of approximately 4.5.
  • the amino acid sequences of the cyanogen bromide fragments of native receptor match perfectly within the deduced amino acid sequence.
  • the open reading frame begins with an ATG that is flanked by the consensus translation initiation sequence GAGATGG for eucaryotic mRNAs as described by Kozak, M. Nucleic Acids Res (1987) 15:8125.
  • the deduced amino acid sequence includes a putative signal, shown underlined, preceding the mature N-terminus Asn-Glu-Arg-etc. Eleven repeats (cadl-cadl 1) are shown in the extracellular region upstream of the membrane domain, shown with the heavy underline, at positions 1406-1427. The end of the 11th repeat is shown with an arrowhead. The positions of the five CNBR fragments are also shown under the complete sequence.
  • FIG. 2 compares the BT-R, sequence obtained herein with other members of the cadherin family.
  • the external domain of BT-R is highly repetitive and contains 11 repeats (cadl-cadl 1 ; see Figure 2 A).
  • the other cadherins compared in Figure 2 B are mouse P cadherin (mP EC1); Drosophila fat EC18 (fat EC 18) and protocadherin (PC42 EC2), and Manduca sexta intestinal transporter (HPT-l-EC-1).
  • the eleven repeats of the cadherin motif in BT-R, (cadl-cadl 1) are individually aligned with a single motif sequence from each of the other members of the cadherin family.
  • BT-R conserved residues are boxed.
  • the greatest similarity of BT-R, to the cadherins is with the extracellular repeats of the cadherin motif of mouse P- cadherin, Drosophila/ ⁇ t tumor suppressor and the protocadherins, although homologies are not high (20-40 homology and 30-60 percent similarity).
  • the conserved repeats of BT-R included AXDXD, DXE, DXNDXXP, one glutamic acid residue and two glycine residues ( Figure 2 B). Motifs A/VXDXD, DXNDN are the consensus sequences for calcium binding and two such regions are present in a typical cadherin repeat.
  • BT-R contains a putative cytoplasmic domain of 101 amino acids, smaller than vertebrate cadherin cytoplasmic domains (160 amino acids), and shows no homology to any of the cadherin cytoplasmic domains or to cytoplasmic domains of other proteins to which it has been compared in a current sequence data base.
  • total mRNA was prepared from midguts of M. sexta subjected to Northern blot by hybridization with the antisense 4.8 kb Sad fragment of the BT-R, cDNA clone.
  • the Northern blot analysis was conducted by hybridizing to the antisense probe at 42°C and 50% formamide, 5 X Denhardt's Reagent, 5 X SSCP and 50 ⁇ g/ml salmon sperm DNA. The filter was then washed two times with 1 X SSC + 0.1% SDS and two times with 0.15 X SSC + 0.1% SDS at 42°C. Each wash was roughly 20 minutes.
  • the filter was then exposed to X-ray film for 24 hours.
  • the 4.8 kb probe hybridized to a single 5.6 kb band.
  • the BT-R, clone was translated using rabbit reticulolysate and the resulting translated products were immunoprecipitated with antisera raised against native protein encoded by BT-R,.
  • pBluescript plasmid containing BT-R, cDNA was linearized and transcribed with T 3 polymerase (Pharmacia). The translation was conducted according to manufacturer's instructions with nuclease-treated rabbit reticulolysate (Life Technologies, Inc.).
  • reaction mixture was combined with an equal volume of SDS buffer or lysed with 50 mM Tris buffer containing 1% NP40 and 250 mM NaCl (pH 8.0) for immunoprecipitation. Preimmune serum was used as a control. Translation and immunoprecipitation products were electrophoresed on a 7.5% SDS- polyacrylamide gel fixed, treated with Enhance (Dupont NEN), dried and exposed to
  • Example 3 Recombinant Production and Characteristics of the BT-R, Protein
  • the BT-R, cDNA clone was subcloned into the mammalian expression vector pcDNA3 (Invitrogen) and the construct transfected into COS-7 cells.
  • Membranes isolated from the COS-7 transfectants were solubilized, electrophoresed and ligand blotted with U5 I-CryIAb toxin.
  • the cells were harvested 60 hours after transfection, washed with phosphate-buffered saline and lysed by freezing in liquid nitrogen. Cell membranes were prepared by differential centrifugation as described by Elshourbagy, N.A. et al. JBiol Chem (1993) 266:3873. Control cells were COS-7 cells transfected with pcDNA3.
  • the cell membranes (10 ⁇ g) were separated on 7.5% SDS-PAGE blotted to a nylon membrane and blocked with Tris-buffered saline containing 5% nonfat dry milk powder, 5% glycerol and 1% Tween-20.
  • the nylon membrane was then incubated with n5 I-CryIAb toxin (2 X 10 5 cpm/ml) for two hours with blocking buffer, dried and exposed to X-ray film at -70°C.
  • the labeled toxin bound to a 210 ⁇ 5 kD protein; the 210 kD band was observed only in lanes containing membranes prepared from either M. sexta or COS-7 cells transfected with the BT-R, cDNA construct containing 4810 bp of cDNA comprising the open reading frame.
  • the discrepancy between the 210 kD protein expressed and the calculated 172 kD molecular weight is due to glycosylation of the protein; in vitro translation of the cDNA clone, as described above, which does not result in glycosylation, does produce the 172 kD protein.
  • the COS-7 produced protein was subjected to digestion with N-glycosidase-F by first denaturing the purified protein by boiling in
  • BT-R Identification Of A Fragment Of BT-R, That Binds To A BT Toxin
  • Fig. 1 The full- length wild-type amino acid sequence of BT-R, is provided in Fig. 1 with a block diagram of a possible cadherin- like structure for BT-R, shown in Fig 3.
  • restriction digest sites from the cDNA are provided relative to the positions at which they would disrupt the amino acid coding sequence.
  • This vector contains transcription/translation sequences designed for use in a rabbit reticulocyte lysate (RRL) system.
  • the clone has been analyzed by restriction mapping and mRNA expression (Fig. 4).
  • Lane UP shows the uncut plasmid and lanes NP and XP show restriction digests using Nsil and Xhol, respectively. Nsil is used because it has only one restriction site lying within the Bam-Sac fragment and does not cut anywhere within the pCITE vector.
  • the BSP lane shows the restriction digest of the clone using BamHI and Sad.
  • the digest releases the cloned fragment which separates at about 700 base pairs.
  • the RT1 and RT2 lanes show mRNA transcription from the clone after linearization with Xhol. The mRNA separates at the expected 1350 base pairs. Protein for analysis has been prepared from this clone in two ways. First, an
  • RRL translation kit was employed to produce protein from the mRNA transcription reaction described above.
  • the plasmid was added directly to an RRL based transcription and translation (TNT) coupled kit. Protein production was detected using 35 S-methionine as a tag (Fig. 5).
  • the LCR lane shows production of luciferase protein from mRNA in an RRL kit and the LCT lane is luciferase protein from a plasmid containing the luciferase coding sequence translated in the TNT kit. Both are positive controls to demonstrate that the two translation kits are operational.
  • the major bands for luciferase translation are observed at 66 kDa.
  • the lanes labeled as RR, and RR2 show expression of the polypeptide sequence of the Bam-Sac fragment of BT-R, translated from mRNA in the RRL kit.
  • the lanes TTl and TT2 are translations from the pCITE plasmid containing the Bam-Sac fragment from the TNT kit. All four lanes possess a major band at 30 kDa which is the expected size of the Bam-Sac fragment with the addition of a coded antibody tag called S-tag.
  • S-tag is part of the multicloning site of pCITE. The clone was then tested for its ability to bind the insecticidal toxin CrylAb.
  • BBMV is wild-type BT-R, prepared from the midgut brush border membrane vesicles (BBMV) of M. sexta, and, is used as a positive control.
  • RBK and TBK are RRL and TNT control reactions prepared without mRNA or plasmid present to determine whether proteins endogenous to either kit bind CrylAb.
  • R, and RR2 are translations from the RRL kit and TTl and TT2 are from the TNT kit.
  • a single 30- kDa band appears in each of these lanes. Two are marked by arrows. These bands demonstrate that the Bam-Sac fragment of BT-R, is capable of binding CrylAb insecticidal toxin.
  • a set of truncation mutants of BT-R was prepared through the use of restriction digests.
  • the cDNA was digested at specific sites to remove increasingly larger portions of the C-terminus.
  • the restriction enzymes used were Nsil, BamHI, Nrul, Clal, Xhol and StuI (Figs. 1 and 3).
  • the procedure involved linearizing the plasmid at each one of these sites and transcribing up to the truncation.
  • the shortened mRNAs then were translated in an RRL kit blotted to nitrocellulose and hybridized with 125 I-labeled CrylAb.
  • Translation of the wild-type BT-R, from the cDNA showed binding to a 172-kDa protein band, the expected size of wild- type BT-R,. It also shows smaller bands that bind CrylAb although the nature of these bands has not been determined.
  • Nsil, BamHI, Nrul, Clal, Xhol and StuI restriction digests did not show any binding to CrylAb except in the region where the reticulocytes bind CrylAb.
  • This data demonstrates that the removal of the last 100 amino acids from wild type BT-R, by Nsil restriction results in the loss of the ability of BT-R, to bind CrylAb. This localizes the toxin binding site on the BT-R, clone and provides a soluble fragment of the receptor that can be used in toxin and other binding studies.
  • Bam-Sac fragment A clone of a fragment of BT-R, called the Bam-Sac fragment, has been prepared. It was prepared using BamHI and Sad restriction digests (Fig. 1) and cloning of the resulting fragment into a vector called pCITE. The polypeptide sequence was translated and tested for binding to the insecticidal toxin CrylAb ( Figure 8). The Bam-Sac fragment binds to CrylAb, providing first insight into the location of the CrylAb binding site within the BT-R, sequence. It lies in the last 234 C-terminal amino acids. This evidence is further supported by a set of truncation mutants that has been prepared. Removal of the 100 most C-terminal amino acids from wild type BT-R, results in the loss of CrylAb binding. The C-terminal end of
  • BT-R is the location of the CrylAb binding site.
  • Example 6 Identification Of Homologue of BT-R, That Binds To A BT Toxin Western blots of tissue extracts prepared from Pink bollworm and European corn borer were prepare and probed with labeled Cry la ( Figure 7). The results show that homologues of BT-R, are present in these two insects and can be readily isolated using the methods described herein.

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Abstract

On a obtenu et séquencé l'ADNc codant un récepteur de glycoprotéine, du sphinx du tabac, qui fixe une toxine de Bacillus thuringiensis. La disponibilité de cet ADNc permet de rechercher les ADN codant les récepteurs homologues chez d'autres insectes et organismes ainsi que d'élaborer des techniques d'analyse de la cytotoxicité et de l'affinité de liaison de pesticides potentiels et de mettre au point des procédés pour manipuler les récepteurs homologues naturels et/ou introduits et de détruire ainsi des cellules, tissus et/ou organismes cibles.
PCT/US1998/011868 1997-06-20 1998-06-08 Recepteur pour une toxine de bacillus thuringiensis Ceased WO1998059048A1 (fr)

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CA002292644A CA2292644A1 (fr) 1997-06-20 1998-06-08 Recepteur pour une toxine de bacillus thuringiensis
EP98926445A EP1005547A1 (fr) 1997-06-20 1998-06-08 Recepteur pour une toxine de bacillus thuringiensis
AU78283/98A AU743234B2 (en) 1997-06-20 1998-06-08 Receptor for a bacillus thuringiensis toxin
BR9810217-6A BR9810217A (pt) 1997-06-20 1998-06-08 Receptor para uma toxina do bacillus thuringiensis
NZ501874A NZ501874A (en) 1997-06-20 1998-06-08 Isolation and characterisation of receptors that are bound by members of the BT-toxin family of insecticidal proteins with respect to pesticides and pest resistance

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US6660497B1 (en) * 1999-10-26 2003-12-09 The Board Of Regents, The University Of Texas System Pectinophora gossypiella (pink bollworm) Bacillus thuringiensis toxin receptor BT-R2
US7060491B1 (en) 1999-11-18 2006-06-13 Pioneer Hi-Bred International, Inc. Polynucleotides encoding novel BT toxin receptors from lepidopteran insects
US7029851B2 (en) 2001-03-15 2006-04-18 Clemson University Polynucleotide encoding a gene conferring resistance to Bacillus thuringiensis toxins
US6891085B2 (en) 2001-04-20 2005-05-10 Pioneer Hi-Bred International, Inc. Nucleic acid encoding the FUS6 antimicrobial polypeptide of Agrotis ipsilon and its use to enhance disease resistance in a plant
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NZ501874A (en) 2001-10-26
WO1998059048A1 (fr) 1998-12-30
ZA985372B (en) 1999-02-04
AU7828398A (en) 1999-01-04
BR9810217A (pt) 2000-08-08
EP1005547A1 (fr) 2000-06-07
AU743234B2 (en) 2002-01-24
AR012252A1 (es) 2000-09-27
CA2292644A1 (fr) 1998-12-30

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