SYNTHESIS AND BIOLOGICAL-ACTIVITY OF FLUORESCENT YEAST PHEROMONES

The mating pheromones of Saccharomyces cerevisiae and derivatives of t hese pheromones have been synthesized and tested for biological activi ty in a solution-phase assay. The effects of native alpha-factor and a -factor on the growth of target cells in these assays were identical. A derivative of alpha-factor in which the amino terminus was modified with the fluorescent probe, ino-N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)h exanoyl, was only slightly less active than the unmodified pheromone. Derivatives of a-factor that contain various alkyl groups in place of the farnesyl moiety of the native pheromone were also synthesized and tested for biological activity. A derivative in which the farnesyl moi ety is substituted with an unbranched decyl group exhibited activity i dentical to that of the natural pheromone, whereas a derivative that c ontains an unbranched pentyl group exhibited significantly lower biolo gical activity than native a-factor. The derivatives of a-factor have in addition been modified to incorporate 6-amino-N-(7-nitrobenz-2-oxa- 1,3-diazol-4-yl) at the terminus of the alkyl chains. A derivative wit h the probe attached to a decyl chain displayed activity similar to th at of the native pheromone, whereas the same modification on a pentyl chain produced a derivative with very low activity. The fluorescence s pectra of the modified alpha-factor and a-factors were measured in met hanol, aqueous solution, and aqueous solution containing phospholipid vesicles. The fluorescence of the probes depends on the environment of the pheromones and can be used to monitor the association of the pher omones with the lipid bilayer.