title: Identification of an SP-1-like protein in non-pregnancy serum: isolation using a monoclonal antibody.
abstract: Human SP-1, a glycoprotein synthesized by the placenta during pregnancy, was shown to exist as polymers in maternal serum by a rapid passive transfer immunoblotting technique following conventional agarose electrophoresis. Moreover, the SP-1 polymers in serum were shown to dissociate into one main component upon treatment with 8 M urea prior to electrophoresis. However, an unexpected observation was the existence of an SP-1-like immunoreactive species in male serum with the sensitive immunoblotting technique. This SP-1-like protein in male serum had similar properties to its placentally derived counterpart in pregnancy serum, namely a propensity for complex formation and a reduced electrophoretic mobility following neuraminidase treatment. The relationship between the two SP-1 proteins was demonstrated by isolating them from their respective sera using an immobilized monoclonal antibody raised to purified SP-1 from pregnancy serum. Immunoblotting after sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed the existence of two major SP-1 species in pregnancy serum. These two SP-1 species had apparent molecular weights of 68,000 and 64,000. In addition, there were two minor bands at 35,000 and 32,000. These smaller SP-1 species did not appear to be subunits of the larger entities since they were detectable in the absence of reducing conditions. SDS-PAGE and immunoblotting showed that the immunoaffinity-purified SP-1 species from male and pregnancy sera had similar, but not identical, molecular weights.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D002846:Chromatography, Affinity / Q000379:methods; D002850:Chromatography, Gel / Q000379:methods; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods; D005260:Female; D006801:Humans; D006825:Hybridomas / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C / Q000276:immunology; D008970:Molecular Weight; D011247:Pregnancy; D011257:Pregnancy Proteins / Q000302:isolation & purification*; D011268:Pregnancy-Specific beta 1-Glycoproteins / Q000302:isolation & purification*
chemical_list: D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D011257:Pregnancy Proteins; D011268:Pregnancy-Specific beta 1-Glycoproteins