Sxa2, a carboxypeptidase that degrades extracellular pheromone in fission yeast.

The fission yeast Schizosaccharomyces pombe exists in one of two mating types (Plus or Minus) and conjugation between two haploid cells is controlled by the reciprocal action of diffusible mating pheromones (for review, see 1). Thus, a P-cell releases P-factor and responds to M-factor since it expresses the M-factor receptor while an M-cell releases M-factor and responds to P-factor. Exposure to pheromone causes changes that prepare the cell for mating but persistent stimulation does not cause a continuous response as the cells recover and adapt to the presence of the pheromone (2.3). One approach to understanding the recovery process is to characterise mutants that are unable to adapt to the pheromone.