title: A novel structural class of toxins: the methionine-rich peptides from the venoms of turrid marine snails (Mollusca, Conoidea).
abstract: The objective of this investigation was to purify and characterize polypeptides from the venom ducts of the turrid snails Polystira albida and Gemmula periscelida (superfamily: Conoidea, family: Turridae), collected in Mexican waters. Venoms of other groups in the superfamily (family: Conidae, genus: Conus) have peptide toxins ('conotoxins'), but no venom components have been characterized from any turrid species. Crude venoms were fractionated using reversed-phase high performance liquid chromatography, and one major component from each venom was characterized. In contrast to most conotoxins, the polypeptides characterized contain a high proportion of Met, Tyr and Arg residues, and few, if any, Cys residues. The two peptides had some regions of homology, but were not significantly similar to other peptides. Both peptides are predicted to contain alpha-helical structures, and the peptide from P. albida is predicted to form a coiled-coil motif. This structural motif could provide conformational stability for these turrid venom components ("turritoxins"), which in the case of conotoxins is primarily achieved by disulfide bonds. Thus, the first turritoxins characterized are strikingly different from the conotoxins, suggesting divergent biochemical strategies in the venoms of different major groups included in the superfamily Conoidea.
authors.affiliation: Laboratory of Marine Neuropharmacology, Institute for Neurobiology, Universidad Nacional Autónoma de México, Querétaro 76230, Mexico.
authors.forename: Estuardo
authors.initials: E
authors.lastname: López-Vera
authors.forename: Edgar P
authors.initials: EP
authors.lastname: Heimer de la Cotera
authors.forename: María
authors.initials: M
authors.lastname: Maillo
authors.forename: Juan R
authors.initials: JR
authors.lastname: Riesgo-Escovar
authors.forename: Baldomero M
authors.initials: BM
authors.lastname: Olivera
authors.forename: Manuel B
authors.initials: MB
authors.lastname: Aguilar
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D013058:Mass Spectrometry; D008715:Methionine / Q000737:chemistry; D008800:Mexico; D008969:Molecular Sequence Data; D008978:Mollusk Venoms / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D010455:Peptides / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D017433:Protein Structure, Secondary; D012623:Seawater; D020539:Sequence Analysis, Protein; D012908:Snails / Q000737:chemistry*
chemical_list: D008978:Mollusk Venoms; D010455:Peptides; D008715:Methionine