The gene encoding bovine pregnancy-associated glycoprotein-1, an inactive member of the aspartic proteinase family.

Bovine pregnancy-associated glycoprotein 1 (bPAG1) is a member of the aspartic proteinase family. It becomes detectable in maternal serum soon after implantation and is produced specifically in the invasive binucleate cells of the placenta. As a result of a key mutation within its catalytic center, bPAG1 appears to be proteolytically inactive. Its gene consists of nine exons (size range 99-281 bp) and eight introns (87-1800 bp) organized in a manner very similar to those of proteolytically active mammalian aspartic proteinases. The transcription start point (tsp) is located 53 or 54 bp upstream from the start codon (ATG) and 19 bp downstream from a 5'-TATATAA sequence. Southern blot analyses have indicated the presence of two bPAG1 genes. By screening with an antiserum raised against bPAG1, a less common cDNA with 91% sequence identity to the bPAG1 transcript has been isolated from a placental cDNA library and presumably represents the second gene. At least eight other genes with sequences that hybridize relatively weakly to the bPAG1 probe are present in the bovine genome. Despite the similarities in the transcribed portion of the genes encoding PAG1, pepsinogen and other mammalian aspartic proteinases, the sequences upstream from the tsp of bPAG1 are unique.