PURIFICATION AND PARTIAL CHARACTERIZATION OF A FLOCCULIN FROM BREWERS-YEAST

Analysis of a shear supernatant from flocculent, ''fimbriated'' Saccha romyces cerevisiae brewer's yeast cells revealed the presence of a pro tein involved in flocculation of the yeast cells and therefore designa ted a flocculin. The molecular mass of the flocculin was estimated to be over 300 kDa, as judged from sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Gel permeation chromatography of the flocculin yi elded an aggregate with an apparent molecular weight of >2,000. The fl occulin was found to be protease sensitive, and the sequence of its 16 N-terminal amino acids revealed at least 69% identity with the predic ted N tenninus of the putative protein encoded by the flocculation gen e FLO1. The flocculin was isolated from flocculent S. cerevisiae cells , whereas only a low amount of flocculin, if any, could be isolated fr om nonflocculent cells. The flocculin was found to stimulate the flocc ulation ability of flocculent yeast cells without displaying lectinlik e activity (that is, the ability to agglutinate yeast cells).