Biosynthesis and secretion of tremerogen A-10, a polysioprenyl peptide mating pheromone of Tremella mesenterica

Abstract

The biosynthetic pathway of tremerogen A-10, a polyisoprenyl peptide mating pheromone produced by mating type AB cells of the heterobasidiomycetous yeast Tremella mesenterica, was investigated by immunological techniques with antibody specific to the peptide moiety of the pheromone. Using the biological assay and the radioimmunoassay of the pheromone and its related substances, it was suggested that the peptide is synthesized near the end of logarithmic phase of growth with a temporary accumulation of precursors in the cell. The precursors initially appeared in membrane-bound form and were subsequently converted to soluble forms prior to the secretion. The pheromone acquired its biological activity during the secretion. In the presence of tunicamycin or compactin, pheromone production was blocked with accumulation of membrane-bound precursors. Monensin, however, blocked pheromone production with accumulation of soluble precursors. The molecular species which accumulated in the presence of the antibiotics were analyzed by immunoprecipitation followed by sodium dodecyl sulfate/urea/polyacrylamide gel electrophoresis. In the absence of the inhibitors, membrane-bound precursors with molecular masses of 28 kDa [kilodaltons], 12 kDa, 7.8 kDa and 2.8 kDa were found. The precursors which accumulated in the presence of tunicamycin and compactin were the 12-kDa and 28-kDa species, respectively. Membrane-bound very high-molecular-mass precursors were initially formed and their extensive modifications, including glycosylation, farnesylation and proteolytic digestion, probably occur in the membrane. Based on these data, a biosythetic and secretory pathway was postulated.