engleski

Influence of individual proteins on the stability of the Saccharomyces cerevisiae cell wall

Saccharomyces cerevisiae cell wall is composed of a glucan network to which a number of mannoproteins are attached. Mannoproteins are either loosely bound to the wall and can be solubilized by SDS, or strongly bound and can be extracted only upon glucanase treatment, suggesting covalent binding to carbohydrate components of the wall. Most abundant detergent-extractable protein is the Bgl2p protein, while the Ccw12p is major protein among those strongly bound to the wall. The Bgl2p protein shows endoglucanase and glucosyltransferase activity in vitro, indicating a role of this protein in the cell wall glucan assembly, while the Ccw12p protein is not characterised yet. In order to assess possible physiological role of those proteins, mutant strains are constructed by disruption of BGL2 or CCW12 genes. Sensitivity of the cell wall to beta-1,3-glucanase treatment was examined and both mutant strains had increased sensitivity in comparison to the parental strains. However, transformation of mutant strains with episomal plasmid containing CCW12, results in reversion of wild type level of glucanase sensitivity in ccw12, but not in the bgl2 strain. This shows that those two proteins affect cell wall stability by different mechanisms. In addition, it was found that overexpression of CCW12 in the wild type cells did not cause increased stability of the cell wall. Furthermore, possible difference in the cell wall protein anchoring between mutants and their parental strains was studied. Results showed that both mutations decreased level of cross-linking between glucan and mannoproteins.

Yeast cell wall; BGL2; CCW12

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