Structure-activity relationships in the dodecapeptide alpha factor of Saccharomyces cerevisiae

Ten analogues of His-Trp-Leu-Gln-Leu-Lys-Pro-Gly-Gln-Pro-Met-Tyr, the dodecapeptide alpha factor of Saccharomyces cerevisiae, were synthesized by conventional solution phase techniques and purified by using high-performance liquid chromatography. The dodecapeptide was also synthesized attached at its carboxyl terminus to poly(ethylene oxide), a macromolecular protecting group. Analogues in which Lys6 or His1 was modified exhibited high biological activity as evidenced by their ability to elicit aberrant morphologies in a cells of S. cerevisiae. These results suggest that neither a free alpha-amine nor a protonatable side chain at position 6 is necessary for biological activity of the dodecapeptide alpha factor. Although Ala2- and Phe2-dodecapeptides were not biologically active, they competed with the natural alpha factor and several active analogues. Thus binding of the alpha factor is not sufficient to elicit a biological response; it appears that the side chain in position 2 is critical for triggering morphological alterations in a cells.