Ciliate mating types and their specific protein pheromones

The determination of a number of pheromone structures from species of Euplotes provided direct evidence that these cell typespecific signals are represented by families of homologous proteins, consistently with their genetic control through series of single-locus multiple alleles. Due to their structural homology, unequivocally manifested by the organization of similar three-dimensional topologies, pheromones can thus compete with one another to effectively bind to their cells of origin in autocrine fashion, or to other conspecific cells in paracrine fashion. The cell response to these different pheromone interactions will accordingly vary, reproductive (mitotic proliferation) in the former case, mating (sexual) in the latter.