RESUMO
A novel peptide, conorfamide-Sr2 (CNF-Sr2), was purified from the venom extract of Conus spurius, collected in the Caribbean Sea off the Yucatan Peninsula. Its primary structure was determined by automated Edman degradation and amino acid analysis, and confirmed by electrospray ionization mass spectrometry. Conorfamide-Sr2 contains 12 amino acids and no Cys residues, and it is only the second FMRFamide-related peptide isolated from a venom. Its primary structure GPM gammaDPLgammaIIRI-nh2, (gamma, gamma-carboxyglutamate; -nh2, amidated C-terminus; calculated monoisotopic mass, 1468.72Da; experimental monoisotopic mass, 1468.70Da) shows two features that are unusual among FMRFamide-related peptides (FaRPs, also known as RFamide peptides), namely the novel presence of gamma-carboxyglutamate, and a rather uncommon C-terminal residue, Ile. CNF-Sr2 exhibits paralytic activity in the limpet Patella opea and causes hyperactivity in the freshwater snail Pomacea paludosa and in the mouse. The sequence similarities of CNF-Sr2 with FaRPs from marine and freshwater mollusks and mice might explain its biological effects in these organisms. It also resembles FaRPs from polychaetes (the prey of C. spurius), which suggests a natural biological role. Based on these similarities, CNF-Sr2 might interact with receptors of these three distinct types of FaRPs, G-protein-coupled receptors, Na+ channels activated by FMRFamide (FaNaCs), and acid-sensing ion channels (ASICs). The biological activities of CNF-Sr2 in mollusks and mice make it a potential tool to study molecular targets in these and other organisms.
Assuntos
Ácido 1-Carboxiglutâmico/química , Caramujo Conus/química , FMRFamida/química , Venenos de Moluscos/química , Neuropeptídeos/química , Peptídeos/química , Sequência de Aminoácidos , Aminoácidos/análise , Animais , Comportamento Animal/efeitos dos fármacos , Sistema Nervoso Central/efeitos dos fármacos , Sistema Nervoso Central/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos , Peso Molecular , Moluscos , Venenos de Moluscos/isolamento & purificação , Venenos de Moluscos/farmacologia , Atividade Motora/efeitos dos fármacos , Músculos/efeitos dos fármacos , Músculos/fisiologia , Neuropeptídeos/isolamento & purificação , Neuropeptídeos/farmacologia , Peptídeos/isolamento & purificação , Peptídeos/farmacologia , Poecilia , Análise de Sequência de Proteína , CaramujosRESUMO
A novel 31-residue toxin, named as7a, was isolated and characterized from the venom of Conus austini, a vermivorous cone snail collected in the western Gulf of Mexico. The complete amino acid sequence, TCKQKGEGCSLDVgammaCCSSSCKPGGPLFDFDC, was determined by automatic Edman sequencing after reduction and alkylation. The sequence shows six Cys residues arranged in the pattern that defines the O-superfamily of conotoxins, and the sequence motif -gammaCCS-, which has only been found in the gamma-conotoxin family. The molecular mass of the native peptide was determined by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, which confirmed the chemical analyses and suggested a free C-terminus. The purified peptide elicited toxic effects in the freshwater snail Pomacea paludosa after intramuscular injection, but it had no effect when injected intracerebrally into mice. The structural similarity of peptide as7a to other gamma-conotoxins suggests that modulation of pacemaker channels could be responsible for its biological activity.
Assuntos
Conotoxinas/química , Conotoxinas/farmacologia , Sequência de Aminoácidos , Animais , Comportamento Animal/efeitos dos fármacos , Caramujo Conus/química , Caramujo Conus/fisiologia , Comportamento Alimentar , Camundongos , Dados de Sequência Molecular , Venenos de Moluscos/química , Poliquetos , Alinhamento de Sequência , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por MatrizRESUMO
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.