Cell-cell recognition in yeast. Molecular nature of the sexual agglutinin from Saccharomyces kluyveri 17-cells

A previous study of Saccharomyces kluyveri 17-cell sexual agglutinin (alpha-agglutinin), solubilized by zymolyase (beta-glucanase) digestion of 17-cells and purified by affinity adsorption to immobilized 16-cell agglutinin (alpha-agglutinin), suggested that the major active component was a glycoprotein of 60,000 daltons and that a minor active component of 40,000 daltons was also present, possibly the result of proteolysis (Pierce, M., and Ballou, C. E. (1983) J. Biol. Chem. 258, 3576-3582). We now show that both of these active components are proteolytic fragments of a larger form with a molecular weight of 134,000, and that the latter is produced by proteolysis of a still larger species with a molecular weight of more than 200,000. Washed 17-cell wall fragments were labeled with 125I and digested with purified protease-free beta-1,3-glucanase, and the solubilized alpha-agglutinin was precipitated with antiserum raised against purified agglutinin containing a mixture of the 60,000- and 134,000-dalton forms. Gel electrophoresis in sodium dodecyl sulfate revealed a radioactive material with Mr greater than 200,000 that, on digestion with zymolyase containing an active protease, was converted sequentially to radioactive components with Mr = 134,000, 60,000, and 40,000.