THE INCORPORATION OF MANNOPROTEINS IN THE CELL-WALL OF SACCHAROMYCES-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 gl ycosylphosphatidylinositol (GPI) moiety before they become anchored to the wall glucan via a beta 1,6-glucan linkage. The mechanism of the m embrane processing step of cell wall proteins is not known. Here, we r eport that Ascomycete filamentous fungi involved in food spoilage such as Aspergillus, Paecilomyces and Penicillium, also contain GPI membra ne-anchored proteins some of which are processed by an endogenous phos pholipase C activity. Furthermore, similar to the situation in yeast, their cell walls contain mannoproteins which are linked to the glucan backbone through a beta 1,6-glucan linkage. Interestingly, one mould w hich contains a significant amount of non covalently linked beta 1,6-g lucosylated cell wall proteins, is much more sensitive towards beta 1, 3-glucanases and membrane perturbing peptides than the others.