Copines: a ubiquitous family of Ca(2+)-dependent phospholipid-binding proteins.

The copines are a novel family of ubiquitous Ca(2+)-dependent, phospholipid-binding proteins. They contain two Ca(2+)- and phospholipid-binding domains known as 'C2 domains' present in proteins such as protein kinase C, phospholipase C and synaptotagmin. Copines are thought to be involved in membrane-trafficking phenomena because of their phospholipid-binding properties. They may also be involved in protein-protein interactions since they contain a domain similar to the protein-binding 'A domain' of integrins. The biochemistry, gene structure, tissue distribution and possible biological roles of copines are discussed, including recent observations with Arabidopsis that indicate that copines may be involved in cell division and growth.