An immunochemical study of trophoblast-specific beta 1-glycoprotein and its fragments

Trophoblast-specific beta 1-glycoprotein (TSG, SP-1) has been isolated from retroplacental blood serum by the usual techniques. Together with the purified TSG, an antigen (TSGfs) possessing partial immunochemical identity with TSG, has been isolated. This antigen, with molecular mass 25 KD, contains virtually no fucose nor neuraminic acid and differs from TSG in a lower content of arginine, tyrosine and aspartic acid. In addition, a low-molecular weight fragment of the TSG molecule (TSGhs), partially identical immunochemically with TSG and fully identical immunochemically with TSGfs, has been obtained by partial acid hydrolysis of TSG. The partial acid hydrolysis of TSG yields TSGhs and high-molecular weight fragments with molecular masses greater than 160 KD which also exhibit a partial identity with TSG. The results provide evidence for the occurrence of a labile linkage bonding the two parts of the TSG molecule which carry different immunochemical determinants.