The incorporation of mannoproteins in the cell wall of S. cerevisiae and filamentous Ascomycetes

In yeast, glucanase extractable cell wall proteins are anchored to the plasma membrane at an intermediate stage in their biogenesis via a glycosylphosphatidylinositol (GPI) moiety before they become anchored to the wall glucan via a 1,6-glucan linkage. The mechanism of the membrane processing step of cell wall proteins is not known. Here, we report that Ascomycete filamentous fungi involved in food spoilage such as Aspergillus, Paecilomyces and Penicillium, also contain GPI membrane-anchored proteins some of which are processed by an endogenous phospholipase C activity. Furthermore, similar to the situation in yeast, their cell walls contain mannoproteins which are linked to the glucan backbone through a 1,6-glucan linkage. Interestingly, one mould which contains a significant amount of non covalently linked 1,6-glucosylated cell wall proteins, is much more sensitive towards 1,3-glucanases and membrane perturbing peptides than the others.