The contribution of cell wall proteins to the organization of the yeast cell wall

Our knowledge of the yeast cell wall has increased rapidly in the past few years, allowing for the first time a description of its structure in molecu lar terms. Two types of cell wall proteins (CWPs) have been identified that are covalently linked to beta-glucan, namely GPI-CWPs and Pir-CWPs. Both d efine a characteristic supramolecular complex or structural unit. The GPI b uilding block has the core structure GPI-CWP --> beta 1,6-glucan --> beta 1 ,3-glucan, which may become extended with one or more chitin chains. The Pi r building block is less well characterized, but preliminary evidence point s to the structure, Pir-CWP --> beta 1,3-glucan, which probably also may be come extended with one or more chitin chains. The molecular architecture of the cell wall is not fixed. The cell can make considerable adjustments to the composition and structure of its wall, for example, during the cell cyc le or in response to environmental conditions such as nutrient and oxygen a vailability, temperature, and pH. When the cell wall is defective, dramatic changes can occur in its molecular architecture, pointing to the existence of cell wall repair mechanisms that compensate for cell damage. Finally, e vidence is emerging that at least to a considerable extent the cell wall of Saccharomyces cerevisiae is representative for the cell wall of the Ascomy cetes. (C) 1999 Elsevier Science B.V. All rights reserved.