Calcium-Dependent Phospholipid Binding to the C2A Domain of a Ubiquitous Form of Double C2 Protein (Doc2 )

Publisher Website
Google Scholar
Abstract
Rabphilin 3A and Doc2α are synaptic vesicle-associated proteins, and are thought to function as Ca2+ sensors in neurotransmitter release. If either rabphilin 3A or Doc2α plays a role in membrane trafficking, like the synaptotagmins, then non-neural forms should be present. Here we describe the isolation of a mouse cDNA which encodes a novel Doc2 homologue (Doc2β) that is present in all tissues. The encoded protein, which is highly homologous to human Doc2α (70% identity), is composed of 412 amino acids with a calculated relative molecular mass (Mr) of 45,837. The sequence identity is especially high in two C2 domains (74% in C2A and 84% in C2B). Northern and Western blot analyses have shown that Doc2£ is expressed in all cell lines and tissues tested. Ca2+-dependent phospholipid binding assaying of recombinant fusion proteins revealed that the single C2A domain, but not the C2B domain, of Doc2β binds phosphatidycholine and phosphatidylserine (2.5 : 1, w/w) liposomes. The binding is Ca2+-dependent, with an EC50 value of approximately 1 μM and a Hill coefficient of approximately 3, which are comparable to those of synaptotagmins, rabphilin 3A and Doc2α. Our results suggest that Doc2β is involved in constitutive membrane trafficking.

This publication has 0 references indexed in Scilit: