Purification and characterization of a Ca2+-dependent membrane peptidase involved in the signaling of mating pheromone in Rhodosporidium toruloides

The sxa2-dependent inactivation of the P-factor mating pheromone in the fission yeast Schizosaccharomyces pombe

Haploid cells of the fission yeast Schizosaccharomyces pombe exist in one of two mating types, referred to as M and P. Conjugation occurs between cells of opposite mating type and is controlled by the reciprocal action of diffusible pheromones. Loss of function of the sxa2 gene in M cells causes hypersensitivity to the P-factor mating pheromone and a reduction in mating efficiency. Here we demonstrate the secretion of an sxa2-dependent carboxypeptidase that inactivates P-factor by removal of the C-terminal leucine residue.

Degradation of a-factor by a Saccharomyces cerevisiae alpha-mating-type-specific endopeptidase: evidence for a role in recovery of cells from G1 arrest

Mating response between opposite mating types of Saccharomyces cerevisiae is dependent upon alpha factor, a tridecapeptide, and a-factor, an isoprenylated, methyl esterified dodecapeptide whose interaction with the alpha target cell has not been characterized. We report on the first biochemical and physiological evidence of an alpha-mating-type-specific a-factor-degrading activity. Radioiodinated a-factor was used to identify the a-factor-degrading activity, which is cell associated, endoproteolytic, and not required for response to pheromone. a-factor degradation was not energy dependent, nor did it require pheromone internalization or interaction with its receptor. Phenylmethylsulfonyl fluoride and tosyl-L-arginyl-methyl ester inhibited degradation of a-factor and increased the time required by alpha cells to recover from a-factor-induced growth arrest and morphological alteration, providing evidence that a-factor degradation plays a role in the recovery of alpha cells from the pheromone response.

Degradation of a-factor by a Saccharomyces cerevisiae alpha-mating-type-specific endopeptidase: evidence for a role in recovery of cells from G1 arrest

Mating response between opposite mating types of Saccharomyces cerevisiae is dependent upon alpha factor, a tridecapeptide, and a-factor, an isoprenylated, methyl esterified dodecapeptide whose interaction with the alpha target cell has not been characterized. We report on the first biochemical and physiological evidence of an alpha-mating-type-specific a-factor-degrading activity. Radioiodinated a-factor was used to identify the a-factor-degrading activity, which is cell associated, endoproteolytic, and not required for response to pheromone. a-factor degradation was not energy dependent, nor did it require pheromone internalization or interaction with its receptor. Phenylmethylsulfonyl fluoride and tosyl-L-arginyl-methyl ester inhibited degradation of a-factor and increased the time required by alpha cells to recover from a-factor-induced growth arrest and morphological alteration, providing evidence that a-factor degradation plays a role in the recovery of alpha cells from the pheromone response.

The role of perireceptor events in chemosensory processes

In a review of vertebrate olfaction, Getchell et al. coined the term 'perireceptor events' to denote processes, ancillary to both receptor activation and transduction, that influence the entry, exit or residence time of odorant molecules in the receptor environment. The present review describes recent advances in our understanding of perireceptor events and shows that these processes are integral components of chemical sensing systems of organisms as diverse as bacteria, slime molds, yeast, insects, crustaceans and mammals. Moreover, it emphasizes that perireceptor processes are essential components of chemical sensing systems, rather than simply interesting adjuncts to the 'main events' of receptor activation and transduction.

Interaction with phospholipids of a membrane thiol peptidase that is essential for the signal transduction of mating pheromone in Rhodosporidium toruloides

Interaction with phospholipids of a membrane thiol peptidase [referred to as trigger peptidase (TPase), T. Miyakawa et al. (1987) J. Bacteriol. 169, 1626-1631] that plays a key role in the signalling of a lipopeptidyl mating pheromone at the cell surface of pheromone-target cell (mating type a) of Rhodosporidium toruloides was studied. The activity of highly purified TPase which requires phospholipids was restored by reconstitution of the enzyme into liposomes prepared with phospholipids extracted from the yeast cell. The presence of Ca2+ was essential for both the reconstitution process and the catalytic reaction of TPase. Triton X-100 mixed micelles containing phospholipids also activated the enzyme. The specificity and stoichiometry of activation by phospholipids was investigated by determination of TPase in the presence of mixed micelles that contained defined classes and numbers of phospholipid molecules in the Triton X-100 micelles. It was demonstrated that TPase is activated by mixed micelles containing 2-6 molecules of phosphatidylserine or phosphatidylethanolamine. Other phospholipids of the membranes of this organism, such as phosphatidylcholine and phosphatidylglycerol, had little effect on activation, indicating that the amino group of the phospholipids may be required for the function of TPase. Direct evidence for the interaction of TPase and Triton X-100/phosphatidylserine mixed micelles was obtained by molecular sieve chromatography on Sephacryl S-200. These data established that a phospholipid bilayer is not a requirement for TPase activation, and that the purified enzyme can be activated by a relatively small number of phospholipid molecules of specific classes.