Improved Purification and N-Terminal Amino Acid Sequence Determination of the Contact Site A Glycoproteinof Dictyostelium discoideum

Abstract

On aggregating cells of D. discoideum a specific glycoprotein is expressed which is absent from growth phase cells of this organism. The glycoprotein is related to cell surface antigens, called contact sites A, that are defined by their reaction with aggregation blocking antibody fragments. An improved purification scheme for the glycopotein is described and its N-terminal sequence is given. The purification was monitored by use of a monoclonal antibody. The contact site A glycoprotein has the properties of an integral membrane protein.