Suppression cloning of the cDNA for a candidate subunit of a presynaptic calcium channel.

A novel strategy, termed suppression cloning, was used to identify a 7.4 kb cDNA encoding a putative subunit of the calcium channels that regulate transmitter release at nerve endings of Torpedo californica. The 585 nt open reading frame of this cDNA encodes a polypeptide of about 21.7 kd that is essential for the expression in frog oocytes of omega-conotoxin-sensitive, dihydropyridine-resistant, calcium channels. Sequence analysis reveals that this protein is closely related to two cloned cysteine string proteins of undertermined function that were recently localized to Drosophila nerve terminals using monoclonal antibodies.