BIOCHEMICAL-CHARACTERIZATION OF A BOVINE OVIDUCT-SPECIFIC SIALO-GLYCOPROTEIN THAT SUSTAINS SPERM VIABILITY IN-VITRO

A bovine oviduct-specific glycoprotein (BOGP) that sustained the viabi lity of bovine spermatozoa in vitro was purified from an extract of bo vine oviducts. The amino-terminal amino acid sequence of BOGP was foun d to be a homologous with that of oviductin, a protein from hamster th at was recently characterized by Mallete and Bleau (1993: Biochem. J. 295, 437-445). Purified BOGP was characterized as a sialo-glycoprotein containing N-linked and O-linked sialo-oligosaccharides side chains w ith galactose, mannose, N-acetyl-D-galactosamine, N-acetyl-D-glucosami ne, fucose and sialic acids in its core protein (57 kDa). Intact BOGP has a wide range of isoelectric points (pIs) from 6.5 to 3.0 but a nar row range of molecular masses around 95 kDa. On isoelectric focusing o f neuraminidase-treated BOGP (AS-BOGP), a narrow band with a pI of 9.3 was observed, and the ability of AS-BOGP to maintain sperm viability was negligible. We propose that BOGP is a mucin-type sialo-glycoprotei n with a molecular mass of 72 kDa that contains one N-linked and appro x. 15 O-linked sialo-oligosaccharide chains. These side chains appeare to be important for the maintenance of sperm viability.