The glucanase‐soluble mannoproteins limit cell wall porosity in Saccharomyces cerevisiae

Abstract

The cell wall porosity of batch-grown Saccharomyces cerevisiae was maximal in the early exponential phase and fell off rapidly to lower levels in later growth phases. Treatment of stationary-phase cells with alpha-mannosidase restored wall porosity to the level of cells in early exponential phase. When cells in the early exponential phase were treated with alpha-mannosidase, or tunicamycin, an inhibitor of N-glycosylation, even higher porosities were obtained. Mutants with truncated mannan side-chains in their wall proteins also had very porous walls. The importance of the mannan side-chains for wall porosity was also seen during sexual induction. Treatment with alpha pheromone, which leads to the formation of wall proteins with shorter mannan side-chains, enhanced wall porosity. Disulphide bridges also affect cell wall porosity. They were predominantly found in the glucanase-soluble wall proteins. Because the main part of the mannan side-chains is also found in this family of wall proteins, our results demonstrate that the glucanase-soluble mannoproteins limit cell wall porosity in yeast.

Architecture and Biosynthesis of the Saccharomyces cerevisiae Cell Wall

“…Association of Sed1 with the wall is dependent on Kre6 (Bowen and Wheals 2004), consistent with anchorage involving b1,6-glucan. SED1 expression is induced in the stationary phase, a time when the wall becomes thicker and more resistant to lytic enzymes (De Nobel et al 1990). Consistent with a protective role in stationary-phase walls, sed1D cells become more sensitive to Zymolyase in that growth phase (Shimoi et al 1998).…”

“…The barrier function of the wall is dependent on growth phase and cultural conditions, with the walls of growing cells being more porous (De Nobel and Barnett 1991). Native glycoproteins such as Cts1, as well as many heterologously expressed soluble glycoproteins with masses up to 400 kDa, can pass through the wall of logarithmically growing cells to the medium, whereas walls of stationary-phase cells are less porous (De Nobel et al 1990;Kuranda and Robbins 1991). The relatively high porosity of walls of logarithmic-phase cells could reflect a lower degree of cross-linking, but the dissolution of septal material that occurs when dividing cells separate could also release wall proteins to the medium (see Order of incorporation of components into the cell wall).…”

Conserved Processes and Lineage-Specific Proteins in Fungal Cell Wall Evolution

“…The polysaccharides are assembled into fibrils and cross-linked to the Ser-rich and Thr-rich glycoproteins through modified GPI-glycans at the C terminal and/or by ester bonds (17,28). Disulfide bonds between glycoproteins also contribute to cell wall integrity (15,48). Many S. cerevisiae wall components and assembly mechanisms have been found in the walls of other fungi, and so S. cerevisiae appears to be a valid general model (24,29,35,38,47).…”

Metallophilic fungi research: an alternative for its use in the bioremediation of hexavalent chromium

“…On the other hand, the capture of chromium in fungi and yeast surfaces has been described as being a result of the union between the components of the cell wall, mostly polysaccharides. Chitin is a linear homopolymer that is linked in b-1,4-acetilglucosamina of filamentous fungi cell walls (Aspergillus), at 10-20%, on average (Bartnicki 1987;de Nobel et al 1990). Glucan is the major structural polysaccharide of the fungal cell wall, and it constitutes approximately 50-60% of the wall dry weight (Nguyen et al 1998;Kapteyn et al 1999).…”