In silicio Identification of Glycosyl-Phosphatidylinositol-Anchored Plasma-Membrane and Cell Wall Proteins of Saccharomyces cerevisiae

Use of the Von Heijne algorithm allowed the identification of 686 open reading frames (ORFs)in the genome of Saccharomyces cerevisiae that encode proteins with a potential N-terminal signal sequence for entering the secretory pathway. On further analysis, 51 of these proteins contain a potential glycosyl-phosphatidylinositol (GPI)- attachment signal. Seven additional ORFs were found to belong to this group. Upon examination of the possible GPI-attachment sites, it was found that in yeast the most probable amino acids for GPI-attachment are asparagine and glycine. In yeast, GPI-proteins are found at the cell surface, either attached to the plasma-membrane or as an intrinsic part of the cell wall. It was noted that plasma-membrane GPI-proteins possess a dibasic residue motif just before their predicted GPI-attachment site. Based on this, and on homologies between proteins, families of plasma-membrane and cell wall proteins were assigned, revealing 20 potential plasma-membrane and 38 potential cell wall proteins. For members of three plasma-membrane protein families, a function has been described. On the other hand, most of the cell wall proteins seem to be structural components of the wall, responsive to different growth conditions. The GPI-attachment site of yeast slightly differs from mammalian cells. This might be of use in the development of anti-fungal drugs.