Synthesis of an O-glycosylated cell surface protein induced in yeast by alpha factor.

A number of cell surface glycoproteins can be specifically and completely released from intact cells of Saccharomyces cerevisiae with 0.5% mercaptoethanol. Among these proteins is one with a molecular mass of 22 kDa, which is synthesized only in haploid a cells treated with the peptide mating pheromone alpha factor. This protein could be radiolabeled in vivo with [2-(3)H]mannose, [(14)C]phenylalanine, and [(35)S]sulfate. Its synthesis and export to the cell surface were not inhibited by tunicamycin. beta-Elimination released almost all radioactivity from the [2-(3)H]mannose-labeled protein, 36% of its radioactivity being recovered subsequently as mannose and 43% as a dimannoside. Evidence is presented that the 22-kDa O-glycosylated protein is a mating-type specific a cell agglutinin.