Source:http://linkedlifedata.com/resource/umls/id/C1511359
NCI: Some isozymes of protein kinase C (PKC) contain a domain, known as C2, of about 116 amino-acid residues which is located between the two copies of the C1 domain (that bind phorbol esters and diacylglycerol) and the protein kinase catalytic domain. Regions with significant homology to the C2-domain have been found in many proteins. The C2 domain is thought to be involved in calcium-dependent phospholipid binding. Since domains related to the C2 domain are also found in proteins that do not bind calcium, other putative functions for the C2 domain such as binding to inositol-1,3,4,5-tetraphosphate have been suggested. The 3D structure of the C2 domain of synaptotagmin has been reported, the domain forms an eight-stranded sandwich constructed around a conserved 4-stranded motif, designated a C2 key. Calcium binds in a cup-shaped depression formed by the N- and C-terminal loops of the C2-key motif. (From Pfam 00168)