Cloning and expression of a new pregnancy-specific beta 1-glycoprotein member

Human pregnancy-specific beta 1-glycoproteins (PSGs) are a group of closely related placental glycoproteins and members of the immunoglobulin superfamily. To study possible functional roles of PSG, three type 1 cDNA clones which encode PSG in a N-A1-A2-B2-C domain arrangement have been characterized in this laboratory. Now, we report the cloning of a type II cDNA (PSG9) which is 1512 bp and encodes a PSG of 332 amino acids in a N-A1-B2-C domain arrangement. In vitro expression experiments demonstrate that PSG9 encodes a 36 kDa nonglycosylated protein which is processed to a glycosylated protein of 46 kDa. Ribonuclease protection analyses show that PSG mRNAs that share sequence similarity with the PSG9 transcript are expressed in both human placenta and placental fibroblasts.