Evidence for the attachment of Hsp150/Pir2 to the cell wall ofSaccharomyces cerevisiaethrough disulfide bridges

Here we present evidence that Hsp150/Pir2, a member of the Pir family of cell wall proteins, can be extracted from the purified cell walls of Saccharomyces cerevisiae by treatment with beta-mercaptoethanol, demonstrating that at least part of this protein is attached to the cell wall through disulfide bridges. We also present evidence that Pir4, another member of this family, is partly secreted to the growth medium. Finally we propose a hypothesis to explain the relationship between the differently localized forms of particular members of the Pir family of cell wall proteins.