Multiple functional domains of the yeast l,3-β-glucan synthase subunit Fks1p revealed by quantitative phenotypic analysis of temperature-sensitive mutants

Abstract

The main filamentous structural component of the cell wall of the yeast Saccharomyces cerevisiae is 1,3-β-glucan, which is synthesized by a plasma membrane-localized enzyme called 1,3-β-glucan synthase (GS). Here we analyzed the quantitative cell morphology and biochemical properties of 10 different temperaturesensitive mutants of FKS1, a putative catalytic subunit of GS. To untangle their pleiotropic phenotypes, the mutants were classified into three functional groups. In the first group, mutants fail to synthesize 1,3-β-glucan at the proper subcellular location, although GS activity is normal in vitro. In the second group, mutants have normal 1,3-β-glucan content but are defective in polarized growth and endocytosis. In the third group, mutations in the putative catalytic domain of Fks1p result in a loss of the catalytic activity of GS. The differences among the three groups suggest that Fks1p consists of multiple domains that are required for cell wall construction and cellular morphogenesis. Copyright © 2010 by the Genetics Society of America.