Incorporation of Sed1p into the cell wall of Saccharomyces cerevisiae involves KRE6

KRE6 (YPR159W) encodes a Golgi membrane protein required for normal beta-1,6-glucan levels in the cell wall. A functional Kre6p is necessary for cell wall protein accumulation in response to changing metabolic conditions. The product of the SEDI (YDR077W) gene is a stress-induced GPI-cell wall protein. Successful incorporation of HA-tagged Sed1p into the cell wall involves KRE6. The double-mutant sed1 kre6 has a reduced growth rate, increased flocculation and increased sensitivity to Zymolyase. A similar phenotype is found in mutants defective in glycosyl-phosphatidyl-insositol (GPI) anchor assembly. These findings support the theory that Kre6p could function as a transglucosylase that allows the incorporation of proteins with a GPI anchor into the cell wall.