Saccharomyces cerevisiae structural cell wall mannoprotein

Abstract

A novel mannoprotein fraction with an average molecular weight of 180 000 has been isolated from Saccharomyces cerevisiae mnn9 mutant cell wall that was solubilized by beta-glucanase digestion. The same material could be extracted from purified wall fragments with 1% sodium dodecyl sulfate. The protein component, 12% by weight, is rich in proline, whereas the carbohydrate, mainly mannose, is about evenly distributed between asparagine and hydroxyamino acids. Endoglucosaminidase H digestion of the isolated mannoprotein reduced its average molecular weight to 150 000, but the mannoprotein, while still embedded in the cell wall, was inaccessible to the enzyme. Biosynthesis and translocation of the mannoprotein were investigated by following incorporation of [3H]proline into this fraction. In the presence of tunicamycin, both mnn9 and wild-type X2180 cells made a mannoprotein fraction with an average molecular weight of 140 000, whereas in the absence of the glycosylation inhibitor, the mnn9 mutant made material with a molecular weight of 180 000 and the mannoprotein made by wild-type cells was too large to penetrate the polyacrylamide gel. Although the cell wall mannoprotein was resistant to heat and proteolytic enzymes, attempts to isolate the carbohydrate-free component failed to yield any characteristic peptide material.

Wall Mannoproteins of the Yeast and Mycelial Cells of Candida albicuns: Nature of the Glycosidic Bonds and Polydispersity of Their Mannan Moieties

“…When this material was P-eliminated and blotted onto nitrocellulose paper, no change in the mobility of the mannoproteins, including the 34 kDa species, was detected (though a significant degradation was evident cf. Frevert & Ballou, 1985) confirming that the 0-mannosidic chains represent a small part of these molecules (Fig. 2).…”

“…These values closely resemble those found in an equivalent material (12% and 8874, respectively) extracted from S . cerevisiae walls by Frevert & Ballou (1985). The carbohydrate component is mainly composed of mannose residues, except for a small but significant amount of glucose.…”

Formation of a New Cell Wall by Protoplasts of Candida albicans: Effect of Papulacandin B, Tunicamycin and Nikkomycin

“…Glucans are the main structural component of the walls, whereas chitin is found only in small amounts (Sullivan et al, 1983). The proteins are grouped in two independent families; one of them (apparent molecular mass 150 kDa or larger) comprises molecules with large polymannose chains (mannan) linked through N-glycosidic bonds, probably connected covalently to the glucan network (Shibata et al, 1983;Frevert & Ballou, 1984;Pastor etal., 1984;Zlotnik eta/., 1984;Elorza eta/., 1985). The other family found in isolated walls comprises a 30 kDa mannoprotein possessing a single N-linked carbohydrate chain and several low molecular mass protein species (between 15 and 80 kDa) most of which lack N-glycosidic linkages: they are associated with the wall structure by non-covalent bonds and their physiological significance is unknown (Pastor et al, 1984;Elorza et al, 1985).…”

Oxidative cell wall damage mediated by bleomycin-Fe(II) in Saccharomyces cerevisiae

“…␤1,6-Glucans may anchor the exterior layer of mannoproteins in the cell wall matrix (13,39,44). Most of the remainder of the wall consists of mannoproteins in which carbohydrate accounts for almost 90% of the weight (13,14). They can be subdivided into two classes.…”