The β‐1,6‐glucan containing side‐chain of cell wall proteins of Saccharomyces cerevisiae is bound to the glycan core of the GPI moiety

Cell wall proteins of Saccharomyces cerevisiae are anchored by means of a β-1,6-glucan-containing side-chain. It is not known whether this chain is linked to the protein part (e.g. through carbohydrate side-chains) or to the glycosylphosphatidylinositol (GPI) moiety of cell wall proteins. An IgA protease recognition site was introduced in Cwp2p, a β-1,6-glucosylated cell wall protein, immediately N-terminal from the omega amino acid (the attachment site of the GPI moiety). Proteolytic cleavage of this site revealed that the β-1,6-glucan epitope was not linked to the protein part. We conclude that neither N- or O-glycosylation is involved in β-glucosylation of cell wall proteins. This confirms that the glycan core of the GPI moiety is the probable β-1,6-glucan attachment site.