engleski

The role of proteolytic processing in the covalent attachment of Scw4p in the Saccharomyces cerevisiae cell wall

Yeast cell wall contains proteins that are noncovalently (Scw-proteins) or covalently (Ccw-proteins) bound to β-1, 3-glucan, the latter either through GPI-anchors and β-1, 6-glucan, or by alkali labile ester linkages between γ-carboxyl groups of glutamic acid and hydroxyl groups of glucoses (Pir-proteins, extracted from the cell wall by mild alkali). It was previously shown that one of the most abundant Scw protein, Scw4p is partly also covalently linked to the cell wall. In this work it was shown that non-covalently bound Scw4p underwent the proteolytic processing, while the covalently bound Scw4p was not processed, indicating that the proteolytic processing might determine the localization of these two forms of the protein. Results showed that the proteolytic enzymes which might have a role in processing of Scw4p are Kex2p and a family of aspartic proteases called yapsins. Besides, it was shown that the two molecular forms reached the cell surface by different routes, the processed form via Sec14p dependent secretory pathway together with most other cell wall and periplasmic proteins, and the unprocessed form using the Sec14p independent pathway. To try to get a better insight in the biological role of Scw4p, phenotypes of strains overproducing Scw4p were examined. It was found that the overproduction of the proteins led to significantly higher mortality of cells, particularly in the stationary phase of growth, increased sensitivity to Calcofluor White, Congo Red and SDS, and to markedly increased cell size.

Scw4; cell wall proteins

nije evidentirano