Immunoadsorbent isolation of pregnancy-specific β1-glycoprotein from maternal serum

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Abstract
A 3-step procedure for the purification of [human] pregnancy-specific .beta.1-glycoprotein (PS.beta.1G) on a mg scale from maternal serum was developed. The principal purification was achieved by the use of an immunoadsorbent and the remaining impurities were removed by hydroxylapatite chromatography and negative affinity chromatography. The overall procedure resulted in the purification of .apprx. 10 mg of PS.beta.1G which represented .apprx. 21% of PS.beta.1G in 300 ml of serum. The PS.beta.1G was of high purity as shown by analytical polyacrylamide gel electrophoresis [PAGE], sodium dodecyl sulfate-PAGE and immunochemical tests. Experiments by immunoelectrophoresis and gel chromatography indicate that the electrophoretic mobility and relative mass of the purified PS.beta.1G are very similar to those of the native serum protein. Structural analysis of PS.beta.1G suggests that it is composed of 2 identical subunit chains bonded noncovalently. A trimeric structure for PS.beta.1G cannot be ruled out based on the uncertainty of relative mass estimates by gel chromatography in nondenaturing solvent. The anomalous characteristics of a previous purified polymeric form of PS.beta.1G (PS.beta.1G-I) are discussed in relation to the new findings presented here.
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