We report the discovery and initial characterization of the T-superfamily of conotoxins. Eight different T-superfamily peptides from five Conus species were identified; they share a consensus signal sequence, and a co...
详细信息
We report the discovery and initial characterization of the T-superfamily of conotoxins. Eight different T-superfamily peptides from five Conus species were identified; they share a consensus signal sequence, and a conserved arrangement of cysteine residues (- -CC- -CC-). T-superfamily peptides were found expressed in venom ducts of all major feeding types of Conus; the results suggest that the T-superfamily will be a large and diverse group of peptides, widely distributed in the 500 different Conus species. These peptides are likely to be functionally diverse; although the peptides are small (11-17 amino acids), their sequences are strikingly divergent, with different peptides of the superfamily exhibiting varying extents of post-translational modification. Of the three peptides tested for in vivo biological activity, only one was active on mice but all three had effects on fish. The peptides that have been extensively characterized are as follows: p5a, GCCPKQMRCCTL*; tx5a, γCCγDGW+CCT§AAO; and au5a, FCCPFIRYCCW (where γ = γ-carboxyglutamate, W^+ = bromotryptophan, O = hydroxyproline, T§ = glycosylated threonine, and * = COOH-terminal amidation). We also demonstrate that the precursor of tx5a contains a functional γ-carboxylation recognition signal in the -1 to -20 propeptide region, consistent with the presence of γ-carboxyglutamate residues in this peptide.
Conotoxins are multiple disulfide-bonded peptides isolated fk om marine cone snail venom. These toxins have been classified into several families based on their disulfide pattern and biological properties. Here, we re...
详细信息
Conotoxins are multiple disulfide-bonded peptides isolated fk om marine cone snail venom. These toxins have been classified into several families based on their disulfide pattern and biological properties. Here, we report a new family of Conus peptides, which have a novel cysteine motif. Three peptides of this family (CMrVIA, CMrVIB, and CMrX) have been purified from Conus marmoreus venom, and their structures have been determined. Their amino acid sequences are VCCGYKLCHOC (CMrVIA), NGVCCGYKLCHOC (CMrVIB), and GICCGVSFCYOC (CMrX), where O represents 4-transhydroxyproline. Two of these peptides (CMrVIA and CMrX) have been chemically synthesized Using a selective protection and deprotection strategy during disulfide bond formation, peptides with both feasible cysteine-pairing combinations were generated. The disulfide pattern (C-1-C-4, C-2-C-3) in native toxins was identified by their co-elution with the synthetic disulfide-isomeric peptides on reverse-phase high pressure liquid chromatography. Although cysteine residues were found in comparable positions with those of alpha -conotoxins, these toxins exhibited a distinctly different disulfide bonding pattern;we have named this new family "lambda -conotoxins." CMrVIA and CMrX induced different biological effects when injected intra-cerebroventricularly in mice;CMrVIA induces seizures, whereas CMrX induces flaccid paralysis. The synthetic peptide with lambda -conotoxin folding is about 1150-fold more potent in inducing seizures than the mispaired isomer with alpha -conotoxin folding Thus it appears that the unique disulfide pattern, and hence the "ribbon" conformation, in lambda -conotoxins is important for their biological activity.
暂无评论