Pregnancy Specific Beta-1-Glycoprotein 4 (PSG4)

The human pregnancy-specific glycoproteins (PSGs) are a family of proteins that are synthesized in large amounts by placental trophoblasts and released into the maternal circulation during pregnancy. Molecular cloning and analysis of several PSG genes has indicated that the PSGs form a subgroup of the carcinoembryonic antigen (CEA) gene family, which belongs to the immunoglobulin superfamily of genes. Members of the CEA family consist of a single N domain, with structural similarity to the immunoglobulin variable domains, followed by a variable number of immunoglobulin constant-like A and/or B domains. PSG9, which had been thought to be a novel gene, is in fact an allelic variant of PSG4 that differs by 6 bp in the coding region. (The allelic variant that had been referred to as PSG9 should not be confused with the PSG9 gene.)