title: CSTX-9, a toxic peptide from the spider Cupiennius salei: amino acid sequence, disulphide bridge pattern and comparison with other spider toxins containing the cystine knot structure.
abstract: CSTX-9 (68 residues, 7530.9 Da) is one of the most abundant toxic polypeptides in the venom of the wandering spider Cupiennius salei. The amino acid sequence was determined by Edman degradation using reduced and alkylated CSTX-9 and peptides generated by cleavages with endoproteinase Asp-N and trypsin, respectively. Sequence comparison with CSTX-1, the most abundant and the most toxic polypeptide in the crude spider venom, revealed a high degree of similarity (53% identity). By means of limited proteolysis with immobilised trypsin and RP-HPLC, the cystine-containing peptides of CSTX-9 were isolated and the disulphide bridges were assigned by amino acid analysis, Edman degradation and nanospray tandem mass spectrometry. The four disulphide bonds present in CSTX-9 are arranged in the following pattern: 1-4, 2-5, 3-8 and 6-7 (Cys6-Cys21, Cys13-Cys30, Cys20-Cys48, Cys32-Cys46). Sequence comparison of CSTX-1 with CSTX-9 clearly indicates the same disulphide bridge pattern, which is also found in other spider polypeptide toxins, e.g. agatoxins (omega-AGA-IVA, omega-AGA-IVB, mu-AGA-I and mu-AGA-VI) from Agelenopsis aperta, SNX-325 from Segestria florentina and curtatoxins (CT-I, CT-II and CT-III) from Hololena curta. CSTX-1/CSTX-9 belong to the family of ion channel toxins containing the inhibitor cystine knot structural motif. CSTX-9, lacking the lysine-rich C-terminal tail of CSTX-1, exhibits a ninefold lower toxicity to Drosophila melanogaster than CSTX-1. This is in accordance with previous observations of CSTX-2a and CSTX-2b, two truncated forms of CSTX-1 which, like CSTX-9, also lack the C-terminal lysine-rich tail.
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Switzerland. johann.schaller@ibc.unibe.ch
authors.forename: J
authors.initials: J
authors.lastname: Schalle
authors.forename: U
authors.initials: U
authors.lastname: Kämpfer
authors.forename: S
authors.initials: S
authors.lastname: Schürch
authors.forename: L
authors.initials: L
authors.lastname: Kuhn-Nentwig
authors.forename: S
authors.initials: S
authors.lastname: Haeberli
authors.forename: W
authors.initials: W
authors.lastname: Nentwig
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003553:Cystine / Q000737:chemistry*; D004220:Disulfides; D013058:Mass Spectrometry; D008956:Models, Chemical; D008969:Molecular Sequence Data; D009498:Neurotoxins / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D021241:Spectrometry, Mass, Electrospray Ionization; D013111:Spider Venoms / Q000737:chemistry*; D013112:Spiders / Q000737:chemistry*
chemical_list: C439583:CSTX-9, Cupiennius salei; D004220:Disulfides; D009498:Neurotoxins; D010455:Peptides; D013111:Spider Venoms; D003553:Cystine