THE PRIMARY STRUCTURE OF BSP-30K, A MAJOR LIPID-BINDING, GELATIN-BINDING, AND HEPARIN-BINDING GLYCOPROTEIN OF BOVINE SEMINAL PLASMA

BSP-30K is a major acidic glycoprotein of bovine seminal plasma. It di splays heparin-, gelatin-, and phospholipid-binding activities. BSP-30 K binds to spermatozoa upon ejaculation and is thought to play a role in sperm capacitation. We have determined its amino acid sequence, dis ulfide bonds, and O-glycosylation sites. BSP-30K consists of 158 amino acids arranged in a mosaic structure. BSP-30K has a unique 48-residue N-terminal extension which includes three 7-8- amino acid repeats and the six O-glycosylated threonine residues. The polypeptide stretch 49 -71 is homologous to type 'A' domains found in heparin-binding protein s from other mammalian species. The C-terminal portion of BSP-30K is o rganized in a tandem of 40-44-residue domains each sharing the consens us pattern of the gelatin-binding fibronectin type II module. The mosa ic structure of BSP-30K suggests that this glycoprotein might be a fac tor contributing to the different sperm-capacitating effects exerted b y heparin in different mammalian species.