Characterization of a disulphide-bound Pir-cell wall protein (Pir-CWP) of Yarrowia lipolytica

In this work we have studied the disulphide-bound group of cell wall mannoproteins of Yarrowia lipolytica and Candida albicans. In the case of Y. lipolytica, SDS-PAGE analysis of the beta-mercaptoethanol-extracted material from the purified cell walls of the yeast form, showed the presence of a main polypeptide of 45 kDa and some minor bands in the 100-200 kDa range. This pattern of bands is similar to that obtained in identical extracts in Saccharomyces cerevisiae (Moukadiri et al., 1999), and besides, all these bands cross-react with an antibody raised against beta-mercaptoethanol-extracted material from the purified cell walls of S. cerevisiae, suggesting that the 45 kDa band could be the homologue of Pir4 of S. cerevisiae in Y. lipolytica. To confirm this possibility, the amino-terminal sequences of two internal regions of the 45 kDa protein were determined, and degenerate oligonucleotides were used to clone the gene. The gene isolated in this way codes a 286 amino acid polypeptide that shows homology with the Pir family of proteins of S. cerevisiae (Russo et al., 1992; Toh-e et al., 1993), accordingly we have named this gene YlPIR1. Disruption of YlPIR1 led to a slight increase in the resistance of the cells to calcofluor white, Congo red and zymolyase, but did not cause changes in cell morphology, growth rate or morphological transition.