Differential glycosylation of the components of the bovine trophoblast protein-1 complex.

The bovine trophoblast protein-1 complex, a major secretory product of the day 17 to 18 conceptus, has been implicated in extension of luteal lifespan during early pregnancy. This glycoprotein complex, identifiable by immunoprecipitation procedures utilizing rabbit antiserum to ovine trophoblast protein-1, exists as seven isomers of two size classes (22 and 24 kDa). Culture of embryos with tunicamycin demonstrated that the isomers are N-linked glycoproteins, as deglycosylated products migrate as a single band (18 kDa) during electrophoresis. Culture with deoxymannojirimycin indicated that the 24 kDa form is complex in nature, whereas treatment with endoglycosidase H and lectin chromatography indicated that the 22 kDa form is a high-mannose type glycoprotein. These results indicate that molecular weight variants of bovine trophoblast protein-1 arise as a single translation product that undergoes differential post-translational glycosylation.