title: Structural characterization of five post-translationally modified isomorphs of a novel putative delta-conotoxin from the vermivorous snail Conus delessertii from the Mexican Caribbean Sea.
abstract: A novel peptide, de7b, was isolated from the venom of Conus delessertii, a worm-hunting species collected in the Caribbean Sea off the Yucatan Peninsula. Its primary structure was determined by automated Edman degradation and confirmed by mass spectrometry: it contains 28 amino acids, including six Cys residues. Peptide de7b is the second, O-conotoxin-like peptide isolated from the venom of this species, and it exists in different post-translationally modified isomorphs, some of which contain gamma-carboxy-glutamate (gamma) and/or 4-hydroxy-proline (O) at positions 4, 7, and/or 14. Its primary structure is DCI(P/O)GG(E/gamma)NCDVFR(O/P)YRCCSGYCILLLCA, with molecular masses varying from 3078.6 to 3154.6Da, depending on the number and kind of modified amino acid residues. Peptide de7b shows significant sequence identity with several O-conotoxins purified and biologically characterized from molluscivorous and piscivorous cone snails of the Indo-Pacific region, the tropical Atlantic and Eastern Pacific Oceans, especially with the delta-conotoxins but also with the omega-conotoxins from molluscivorous species, which suggests that it might affect voltage-gated Na(+) or Ca(2+)channels. Peptide de7b has 32% sequence identity with putative gamma-conotoxin de7a, previously characterized from the same species; both peptides contain the same number of amino acid residues and of non-Cys residues between the pairs of consecutive Cys residues. However, these peptides have charge differences at seven positions within the N-terminal half indicating that they might have distinct molecular targets that remain to be identified.
authors.affiliation: Laboratorio de Neurofarmacología Marina, Departamento de Neurobiología Celular y Molecular, Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, Querétaro 76230, Mexico. maguilar@servidor.unam.mx
authors.forename: Manuel B
authors.initials: MB
authors.lastname: Aguilar
authors.forename: Artemisa
authors.initials: A
authors.lastname: Flores-Torres
authors.forename: César V F
authors.initials: CV
authors.lastname: Batista
authors.forename: Andrés
authors.initials: A
authors.lastname: Falcón
authors.forename: Estuardo
authors.initials: E
authors.lastname: López-Vera
authors.forename: Edgar P Heimer
authors.initials: EP
authors.lastname: de la Cotera
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D020916:Conotoxins / Q000737:chemistry* / Q000235:genetics; D052078:Conus Snail / Q000235:genetics*; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics; D011499:Protein Processing, Post-Translational; D016415:Sequence Alignment
chemical_list: D020916:Conotoxins; D020033:Protein Isoforms; C540920:delta-conotoxin de7b, Conus delessertii