A peptidyl factor named α substance-IA, which induces sexual agglutinability in α type cells of the heterothallic Saccharomyces cerevisiae, was found to be composed of twelve amino acid residues. Further, the amino acid sequence was elucidated by the combined application of the Edman-dansyl procedure and the cleavage reaction with cyanogen bromide to be H-His-Trp-Leu-Gln-Leu-Lys-Pro-Gly-Gln-Pro-Met-Tyr-OH.
