[The purification of pregnancy specific beta 1-glycoprotein (SP1) from third trimester serum and the immunological identification of gamma-component of SP1].

This paper describes the SP1 purification procedures with high recovery from third trimester serum and the finding of a new SP1 antigen with gamma-mobility (tentatively called SP1-gamma). The serum was salted out at 40% saturation with ammonium sulfate and this was followed by Sephadex G-150, DEAE-cellulose, SP1-negative affinity chromatography and the mono-Q column of FPLC system. The anti-serum for the immunoadsorption techniques was made from the fractionated male serum. By these procedures, the final SP1 preparation was obtained in a yield of 16% and with a purity of 99%. The purified SP1 (SP1-beta) had beta-mobility and its molecular weight approximated 72,000 in SDS polyacryl-amide gel electrophoresis. The isoelectric points (pI) ranged between 3.80 to 4.55 using isoelectric focusing and the site at pI 4.15 was strongly stained. Another SP1, which passed through DEAE-cellulose with a low salt concentration, was detected in the gamma-region by means of immunoelectrophoresis using anti-SP1 serum. It was ascertained that the SP1-gamma was different from the SP1-beta treated with neuraminidase. The SP1-gamma precipitation fusing with SP1-beta could be observed even in pregnant serum by usual immunoelectrophoresis. The SP1-gamma preparation showed at least four pIs of 5.3, 5.5, 5.65 and 5.8.