Penta-EF hand, calcium binding motifs, found in Drosophila melanogaster calpain-C (CalpC) and similar proteins
CalpC, also termed calcium-activated neutral proteinase homolog C (CANP C), is a catalytically inactive homolog of CalpA and CalpB found in Drosophila. It is strongly expressed in the salivary glands. In contrast with CalpA and CalpB, both of which are closely related to that of vertebrate calpains, and they share similar domain architecture, which consists of four domains: the N-terminal domain I, the catalytic domain II carrying the three active site residues, Cys, His and Asn, the Ca2+-regulated phospholipid-binding domain III, and penta-EF-hand Ca2+-binding domain IV. CalpC is a truncated calpain form missing domain I and about 20 residues from domain II. Moreover, due to all three mutated active site residues (Cys to Arg, His to Val and Asn to Ser), it may not have proteolytic activity.