ISOLATION, CHARACTERIZATION, AND PRIMARY STRUCTURE OF 3 MAJOR PROTEINS OBTAINED FROM MYTILUS-EDULIS SPERM

Acrosomal proteins from Mytilus edulis sperms were separated into ll f ractions by reverse phase HPLC. The three major proteins, named M3, M6 , and M7, showed strong egg vitelline coat lysin and first polar body releasing activities. The amino acid sequences of these proteins were determined. M6 and M7 were composed of 180 amino acid residues and sho wed high sequence homology (76%), while M3 was composed of 149 residue s and showed 26% homology with M6 and M7. The disulfide linkage motif of the three proteins was similar and resembled the carbohydrate recog nition domain (CRD) of C-type lectin. The C-terminal half of these pro teins showed sequence homology with CRD of C-type lectins, but no homo logy with vitelline coat lysins of other mollusks. The proteins bound to asialofetuin-Sepharose in the presence of Ca2+ and were eluted with EDTA, indicating that they are Ca2+-dependent carbohydrate-binding pr oteins.