Another brick in the wall? Recent developments concerning the yeast cell envelope

Abstract

To a yeast, the cell wall is an important living organelle performing a number of vital functions, including osmotic and physical protection, selective permeability barrier, immobilized enzyme support and cell-cell recognition and adhesion. Our basic model of wall structure involves attachment of secreted mannoproteins to a fibrillar inner layer of beta-glucan. Recent work has emphasised the importance of chitin in lateral walls, examined the mechanisms of attachment of mannoproteins to the various cell wall glucan fractions and elucidated the pathway of beta-glucan synthesis, by means of resistance to glucan-binding killer toxins. The conventional view of wall structure has been challenged by the discovery of a class of GPI-anchored, serine/threonine-rich wall-proteins. It has been suggested, that these proteins are anchored in the plasma membrane, spanning the wall with extended O-glycosylated structures and protruding out into the medium. Examination of these proteins shows a diversity of structures, sizes and behaviour that makes it improbable that these represent a new class of wall proteins. The possible roles of one of these proteins associated with flocculation, Flo1p, are discussed.

β-Glucans, History, and the Present: Immunomodulatory Aspects and Mechanisms of Action

“…According to Stratford (Stratford, 1994), the yeast cell wall resembles reinforced concrete. An armature, representing about 35% of wall mass and formed by fibrils of alkali insoluble β(1→3)-glucan, is dipped into mannoproteins (about 25-35% of wall mass) and bound to the armature through amorphous β-glucan and chitin.…”

Multiple sequence signals determine the distribution of glycosylphosphatidylinositol proteins between the plasma membrane and cell wall in Saccharomyces cerevisiae

“…The structure of the Ser/Thr-rich regions found in many cell wall proteins has been modelled to assume a linear rigid rod-like configuration when glycosylated (Jentoft, 1990;Stratford, 1994). We wished to know whether the effect the Ser/Thr-rich region had on protein distribution between membrane and cell wall was related to glycosylation of the Ser/Thr-rich region.…”

Binding of hemolin to bacterial lipopolysaccharide and lipoteichoic acid. An immunoglobulin superfamily member from insects as a pattern-recognition receptor

“…The binding was concentration-dependent and was not saturated at 50 lgAEmL . Yeast cell walls are composed primarily of b-1,3-glucans and mannans [27]. Zymosan, a yeast cell-wall preparation that contains glucan, mannan and chitin, decreased binding of hemolin to LPS by 61% (Fig.…”