Mating reaction in Saccharomyces cerevisiae. IX. Regulation of sexual cell agglutinability of a type cells by a sex factor produced by alpha type cells.

A diffusible sex-specific substance called alpha substance-I (alphaS-I) was isolated from culture filtrate of alpha type strains of the yeast Saccharomyces cerevisiae. The isolated alphaS-I, an oligopeptide, induced sexual cell agglutinability in inducible alpha type strains and enhanced the agglutinability in constitutive a type strains. The induction of sexual agglutinability was detected in 30 min and reached maximum in 90 min, when 0.2 mug/ml of alphaS-I was added to inducible a type cells. The a type-specific factor responsible for sexual cell agglutination, called a type agglutination factor (aAF), was shown to be produced during the induction or the enhancement of agglutinability of a type cells by alphaS-I. The aAF produced in response to alphaS-I was not different in the susceptibility to proteolytic enzymes and disulfide-cleaving agents from those produced constitutively in the absence of alphaS-I.