Suppression Cloning of the cDNA for a Candidate Subunit of a Presynaptic CalciumChannel

摘要

This paper describes the use of a novel cDNA cloning strategy that was applied toisolate the cDNA encoding an essential subunit or regulatory component of presynaptic calcium channels. The 7.4 kb clone that was isolated encodes a small protein of 195 amino acids that is distinguished by the presence of a region of particularly abundant cysteine residues. Interestingly, a homologous clone had previously been identified in Drosophila where the cloning was accomplished using a monoclonal antibody that targeted a nerve-terminals-specific antigen of unknown function. The dual lines of evidence from the antibody localization of related protein at Drosophila nerve ending membranes along with our physiological evidence of the essential role of these proteins in preserving the functional expression in frog oocytes of omega-conotoxin-sensitive, dihydropyridine-resistant (N-type) calcium channels strongly suggests that these polypeptides play a hitherto undiscovered role in the operation of these ion channels. Cloning of the CDNA for the first vertebrate homolog of these cysteine string proteins will enable us to explore in greater detail their function at nerve endings.... Calcium channels, Omega-conotoxin, CDNA cloning, Xenopus oocytes, Protein expression.