Yeast beta-glucan synthesis: KRE6 encodes a predicted type II membrane protein required for glucan synthesis in vivo and for glucan synthase activity in vitro

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 88; no. 24; pp. 11295 - 11299
• Main Authors: ROEMER, T, BUSSEY, H
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 15.12.1991; National Acad Sciences
• Subjects: activity; Alleles; Amino Acid Sequence; beta -glucan; Biological and medical sciences; biosintesis; biosynthese; biosynthesis; Cell Membrane - enzymology; Cell walls; Chromosome Deletion; Cloning, Molecular; code genetique; codigo genetico; Diploidy; Fundamental and applied biological sciences. Psychology; gene products; genes; Genes, Fungal; genetic code; genetica; genetics; genetique; Genomic Library; glucan synthase; glucane; glucano; Glucans; Glucans - biosynthesis; Glucosyltransferases - genetics; Glucosyltransferases - metabolism; KRE6 gene; levadura; levure; liasas; lyase; lyases; membrana; membrane; Membrane Proteins; membranes; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Mutagenesis, Insertional; mutant; mutantes; mutants; nucleotide sequence; Phenotypes; Plasmids; Polymers; predictions; proteinas; proteine; Proteins; Restriction Mapping; Saccharomyces cerevisiae; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae - genetics; Schizosaccharomyces pombe Proteins; synthesis; Yeasts; Fungi; Glucan; Membrane protein; Yeast; Enzymatic activity; Ascomycetes; Biosynthesis; Polysaccharide; Saccharomyces cerevisiae; Thallophyta
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.88.24.11295

The KRE6 gene product is required for synthesis of the major beta-glucans of the yeast cell wall, as mutations in this gene confer reduced levels of both the (1 leads to 6)- and (1 leads to 3)-beta-D-glucan polymers. Cloning and sequencing of KRE6 reveals a gene encoding a predicted 80-kDa protein with a central transmembrane domain and the topology of a type II membrane protein. Null mutants of KRE6 grow slowly, have larger cells, and show a reduction in alkali-insoluble wall glucans. The mutants show good viability and are not osmotically sensitive, but they are more susceptible to beta-glucanase digestion and mechanical stress than wild-type cells. The specific activity of the GTP-dependent, membrane-associated, in vitro (1 leads to 3)-beta-glucan synthase is reduced 50% in kre6 null mutants, and this reduction correlates with the mutation in meiotic tetrads. Transformants of kre6 null mutants with a KRE6 gene expressed from a centomere-based vector show a 4- to 5-fold increase in vitro (1 leads to 3)-beta-glucan synthase activity over transformants with the vector alone. The phenotype and structure of the KRE6 product, Kre6p, suggest that Kre6p may be a beta-glucan synthase, and if so, it implies that beta-glucan synthases are functionally redundant in yeast. Alternatively, Kre6p may be part of a single multiprotein glucan synthase or modulate its activity. Use of KRE6 should permit a genetic analysis of eukaryotic (1 leads to 3)-beta-glucan synthesis.