Interaction of both the C2A and C2B domains of rabphilin3 with Ca2+ and phospholipid.

Rabphilin3, a downstream target molecule of the Rab3 subfamily small G proteins, has two C2 domains (the C2A and C2B domains) at its C-terminal region and is implicated in Ca(2+)-dependent neurotransmitter release. Rabphilin3 interacts with Ca2+ and phospholipid at its C2 domain, but it remains to be clarified which domain, the C2A or C2B domain, interacts with these compounds. We have found here that both the C2A and C2B domains interact with Ca2+ with similar kinetics but interact with phospholipid with slightly different kinetics.