Copine III (CPNE3)

CPNE3 contains 2 N-terminal C2 domains, like CPNE1, CPNE6, and CPNE7, but these 4 copines have divergent C termini. CPNE3 is 63%, 52%, and 47% identical to CPNE1, CPNE6, and CPNE7, respectively. Northern blot analysis revealed ubiquitous expression of a 5.0-kb transcript. Biochemical analysis showed that CPNE3 appears to possess endogenous kinase activity, although it lacks a classic kinase domain. CPNE3 is phosphorylated on both serine and threonine residues but not on tyrosine residues.The deduced 537-amino acid CPNE3 protein is 65.7% identical to CPNE1. By SDS-PAGE, the in vitro transcribed/translated product of the CPNE3 cDNA had a molecular mass of 65 kD. RT-PCR detected CPNE3 expression in all human tissues examined.