Molecular cloning of an isoform of Doc2 having two C2-like domains.

We previously isolated a novel protein having two C2-like domains known to interact with Ca2+ and phospholipid, and named Doc2 (Double C2). Doc2 is predominantly expressed in brain and is implicated in Ca(2+)-dependent neurotransmitter release. We have isolated here an isoform of Doc2 and named the original one Doc2 alpha and the new one Doc2 beta. Doc2 beta alsp has two C2-like domains and is 61% identical to Doc2 alpha at the amino acid level. In contrast to Doc2 alpha, the Doc2 beta mRNA is expressed ubiquitously. These results indicate that there are at least two isoforms of Doc2, and suggest that Doc2 beta is involved in Ca(2+)-dependent intracellular vesicle trafficking in various types of cells.