Pheromone Receptors (Yeast)

Fungal cells secrete substances (pheromones) that stimulate the ability of haploid cells of different mating types to conjugate, thereby forming diploid cells. Compounds used by various fungal species include terpenes (e.g., Allomyces spp.), steroids (e.g., Achlya spp.), and peptides (many ascomycetes). The best-characterized fungal pheromone receptors are those for the peptide-mating pheromones of the budding yeast, Saccharomyces cerevisiae. These receptors are integral membrane proteins that contain seven highly hydrophobic, and likely α-helical, transmembrane segments. They bind their cognate pheromone at the cell surface, and then activate an intracellular heterotrimeric G protein that initiates a signaling pathway. This pathway induces physiological responses, including the expression of many genes needed to divert cells from the mitotic cell cycle required for vegetative proliferation into a developmental program that permits the fusion of the participating haploid cells. These yeast pheromone receptors are representatives of a very large superfamily that is conserved from yeast to humans.