Role of NaOH-extractable cell wall proteins Ccw5p, Ccw6p, Ccw7p and Ccw8p (members of the Pir protein family) in stability of the Saccharomyces cerevisiae cell wall

The Saccharomyces cerevisiae cell wall contains more than 20 identified man noproteins. Some of them can be released from the wall by hot SDS/mercaptoe thanol treatment and are, therefore, considered as disulphide-linked or non -covalently attached to wall structural components. A number of covalently linked cell wall proteins are released after SDS extraction. They can be di vided into these extractable by glucanases and those which can be released with 30 mM NaOH. The SDS-extractable proteins either possess enzymatic acti vities or are homologues of enzymes, mainly glucanases. Nothing is known, h owever, about the function of co-valently linked proteins. In order to inve stigate the role of NaOH-extractable cell wall proteins, genes encoding all four identified members of this family of Pir proteins, CCW5, CCW6, CCW7 a nd CCW8, were disrupted and the phenotype of the mutants obtained was exami ned. They grew somewhat more slowly, were larger and irregularly shaped, an d showed pronounced susceptibility to cell wall synthesis inhibitors like C alcofluor white and Congo red. In addition, the triple and the quadruple de letants had a decreased mating ability. All these properties were more obvi ous the more of these genes were disrupted, indicating that probably all me mbers of this protein family are at least functionally equivalent in the ce ll wall. Copyright (C) 1999 John Wiley & Sons, Ltd.