Characterization of an Oviductal Glycoprotein Associated with the Ovulated Hamster Oocyte1

Abstract

Hamster oviducts in culture incorporate [35S]-methionine into secretory proteins. One of these proteins is immunoprecipitated by a monoclonal antibody specific to an antigen found in oviductal oocytes but not in ovarian oocytes. This antigen, called oviductin, is progressively added to the oocyte during its transit through the oviduct. Oviductin migrates as a diffuse band with a molecular mass between 160 and 250 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions. The electrophoretic behavior of this protein suggests the presence of polysaccharide side chains. Chemical deglycosylation causes a decrease in molecular mass and removes the antigenic determinant originally present on the glycoprotein. By using the radiation inactivation method, the molecular mass of the core protein has been found to be approximately 44 kDa. These results indicate that the oviduct is an actual site of synthesis of the oviductin. This glycoprotein contains a high proportion of sugar residues, which account for antigenic determinant recognized by the monoclonal antibody.