Purification and molecular cloning of bovine oviduct-specific glycoprotein

A specific 85-97-kDa (95-kDa) glycoprotein was found in bovine oviductal tissue and fluid during the follicular phase. In this study, a 95-kDa bovine oviductal glycoprotein (95-kDa BOGP) was purified by wheat germ agglutinin affinity and Mono-Q ion-exchange column chromatography. The first 29 NH2-terminal amino acid residues were determined by gas-phase microsequencing. A cDNA expression library prepared from poly(A)+ RNA isolated from bovine oviducts was screened with a monoclonal antibody to 95-kDa BOGP. A single positive clone containing a approximately 2-kb cDNA insert was isolated. The coding region contained 1612 bp translating to 537 amino acids. The derived amino acid sequence contained a partial signal sequence of 18 amino acids followed by 29 amino acids that were identical to the NH2-terminal amino acids determined by protein sequencing of purified 95-kDa BOGP. The amino acid sequence predicted a mature protein of 519 amino acids (57,684 daltons) containing one potential N-linked glycosylation site and five cysteines. Northern blot hybridization with a digoxigenin-labeled probe indicated that a single message of approximately 2.5 kb was present in oviductal RNA, and this message was detected in significantly greater amounts in oviductal RNA during the follicular phase than during the luteal phase. The amino acid sequence of a portion of 95-kDa BOGP was highly homologous (71% identity) to that of a baboon oviduct-specific glycoprotein.