Proteolytic processing of Saccharomyces cerevisiae cell wall protein Scw4p

Yeast cell wall contains proteins that are noncovalently (Scw-proteins) or covalently (Ccw-proteins) bound to β-1, 3-glucan, 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). It was previously shown that one of the most abundant Scw protein, Scw4p is partly also covalently linked to the cell wall and that non-covalently bound Scw4p underwent the proteolytic processing, while the covalently bound Scw4p was not processed. Such finding indicates that the proteolytic processing might determine the localization of these two forms of the protein. Proteolytic enzymes which might have a role in processing of Scw4p are Kex2p and a family of aspartic proteases called yapsins. To get a better insight in the processing of Scw4p, different mutations were introduced to SCW4 in the region of predicted processing sites. Besides, native and mutated forms of Scw4p were expressed in kex2 yeast strain and strain with all yapsin genes disrupted (5yps∆) and Scw4p processing was examined.