RESUMO
This communication reviews most of the important findings related to venom components isolated from scorpions and spiders, mainly by means of gene cloning and expression. Rather than revising results obtained by classical biochemical studies that report structure and function of venom components, here the emphasis is placed on cloning and identification of genes present in the venomous glands of these arachnids. Aspects related to cDNA library construction, specific or random ESTs cloning, transcriptome analysis, high-throughput screening, heterologous expression and folding are briefly discussed, showing some numbers of species and components already identified, but also shortly mentioning limitations and perspectives of research for the future in this field.
Assuntos
Peptídeos/metabolismo , Venenos de Escorpião/genética , Venenos de Aranha/genética , Animais , Clonagem Molecular , Etiquetas de Sequências Expressas/química , Etiquetas de Sequências Expressas/metabolismo , Perfilação da Expressão Gênica , Biblioteca Gênica , Ensaios de Triagem em Larga Escala , Peptídeos/genética , Proteômica , Venenos de Escorpião/química , Venenos de Aranha/químicaRESUMO
Among the scorpion venom components whose function are poorly known or even show contrasting pharmacological results are those called "orphan peptides". The most widely distributed are named beta-KTx or scorpine-like peptides. They contain three disulfide bridges with two recognizable domains: a freely moving N-terminal amino acid sequence and a tightly folded C-terminal region with a cysteine-stabilized alpha/beta (CS-alphabeta) motif. Four such peptides and three cloned genes are reported here. They were assayed for their cytolytic, antimicrobial and K (+) channel-blocking activities. Two main characteristics were found: the existence of an unusual structural and functional diversity, whereby the full-length peptide can lyse cells or kill microorganisms, and a C-terminal domain containing the CS-alphabeta motif that can block K (+) channels. Furthermore, sequence analyses and phylogenetic reconstructions are used to discuss the evolution of this type of peptide and to highlight the versatility of the CS-alphabeta structures.
Assuntos
Sobrevivência Celular/efeitos dos fármacos , Defensinas/química , Peptídeos/farmacologia , Bloqueadores dos Canais de Potássio/farmacologia , Venenos de Escorpião/química , Venenos de Escorpião/farmacologia , Animais , Anti-Infecciosos/isolamento & purificação , Anti-Infecciosos/farmacologia , Defensinas/isolamento & purificação , Evolução Molecular , Neurotoxinas , Peptídeos/isolamento & purificação , Bloqueadores dos Canais de Potássio/isolamento & purificaçãoRESUMO
The effect of the skin secretion of the amphibian Siphonops paulensis was investigated by monitoring the changes in conductance of an artificial planar lipid bilayer. Skin secretion was obtained by exposure of the animals to ether-saturated air, and then rinsing the animals with distilled water. Artificial lipid bilayers were obtained by spreading a solution of azolectin over an aperture of a Delrin cup inserted into a cut-away polyvinyl chloride block. In 9 of 12 experiments, the addition of the skin secretion to lipid bilayers displayed voltage-dependent channels with average unitary conductance of 258 ± 41.67 pS, rather than nonspecific changes in bilayer conductance. These channels were not sensitive to 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid or tetraethylammonium ion, but the experimental protocol used does not permit us to specify their characteristics
Assuntos
Animais , Venenos de Anfíbios , Anfíbios , Canais Iônicos , Bicamadas Lipídicas , Pele , Venenos de Anfíbios , Condutividade ElétricaRESUMO
The effect of the skin secretion of the amphibian Siphonops paulensis was investigated by monitoring the changes in conductance of an artificial planar lipid bilayer. Skin secretion was obtained by exposure of the animals to ether-saturated air, and then rinsing the animals with distilled water. Artificial lipid bilayers were obtained by spreading a solution of azolectin over an aperture of a Delrin cup inserted into a cut-away polyvinyl chloride block. In 9 of 12 experiments, the addition of the skin secretion to lipid bilayers displayed voltage-dependent channels with average unitary conductance of 258 +/- 41.67 pS, rather than nonspecific changes in bilayer conductance. These channels were not sensitive to 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid or tetraethylammonium ion, but the experimental protocol used does not permit us to specify their characteristics.