Purification and Partial Characterization of a Factor, a Mating Hormone Produced by Mating‐Type‐a Cells from Saccharomyces cerevisiae

Cells of Saccharomyces cerevisiae exhibiting the a mating type secrete into the culture medium a mating-type-specific hormone activity (a factor), which specifically causes a transient arrest of DNA replication and cell division in cells of the opposite mating type, alpha. Three compounds exhibiting a factor activity have been found in culture filtrates from a cells. The most active compound has been purified more than 10(5)-fold and appears to be homogeneous on the basis of thin-layer chromatography and thin-layer electrophoresis in different systems. We propose that this compound, which exhibits in alpha cells the biological activities that have been attributed to a factor, represents pure a factor. a factor has been characterized as a very hydrophobic undecapeptide with the following amino acid composition: H2N-Tyr (Asx1, Gly1, Ala1, Val1, Ile2, Phe1, Lys1, Trp1, Pro1). Although in their respective target cells the biological effects of a factor and of alpha factor, the corresponding mating hormone of mating-type-alpha cells, are remarkably similar, the primary structures of both hormones appear to be quite different.