Characterization of a glycosylphosphatidylinositol-bound cell-wall protein (GPI-CWP) in Yarrowia lipolytica.

The structure and composition of the cell wall of yeast has so far been studied mainly in Saccharomyces cerevisiae. It is basically made up of three components: beta-glucans, chitin and mannose-containing glycoproteins, also called mannoproteins. Most covalently bound cell-wall mannoproteins belong to the so-called glycosylphosphatidylinositol cell-wall protein (GPI-CWP) family, cell-wall proteins that are bound through the remnant of a GPI residue to 1,6-beta-glucan. The non-conventional yeast Yarrowia lipolytica shares Generally Regarded As Safe (GRAS) status with S. cerevisiae, has some industrial applications and is increasingly being proposed as a host for the production of recombinant proteins and as a model in the study of dimorphism. However, very little information on cell-wall structure and composition is available for this organism. Here is described the isolation and characterization of YlCWP1, a homologue of the CWP1 gene from S. cerevisiae, which encodes a GPI-CWP, and the identification of its gene product. YlCWP1 encodes a 221 aa protein that contains a putative signal peptide and a putative GPI-attachment site. It shows 28.5 % overall identity with Cwp1 of S. cerevisiae and a hydropathy profile characteristic of GPI-CWPs. Disruption of YlCWP1, both in the wild-type and in an mnn9 glycosylation-deficient background, led to the identification of Ylcwp1 as a 60 kDa polypeptide present in cell-wall extracts. To the authors' knowledge, this is the first report of a GPI-CWP in Y. lipolytica, and it suggests that the cell-wall organization of Y. lipolytica is similar to that of S. cerevisiae.