Mutations in the yeast gene KRE1 lead to resistance to the K1 killer toxin of S. cerevisiae. The resistant phenotype is associated with a 40% reduction of the cell wall (1 $ to$ 6)-$ beta$-glucan fraction. Yeast cell wall (1 $ to$ 6)-$ beta$-glucan is a highly branched glucose polymer composed predominantly of linear (1 $ to$ 6)-$ beta$- sc D-linked glucopyranosyl residues. This glucan acts as a receptor for the killer toxin, leading to a concentration of active toxin on the yeast cell surface. The KRE1 gene was cloned by complementation of the kre1-1 mutant allele. The KRE1 gene encodes a serine and threonine rich protein, that is directed into the yeast secretory pathway, where it is highly modified, probably through O-linked glycosylation. Haploid strains with a kre1::HIS3 disruption appear to grow somewhat more slowly than wild type, and show an unusual wall structure when examined using electron microscopy. As with strains that carry a mutant kre1-1 allele those with a kre1::HIS3 disruption show a 40% reduced level of cell wall (1 $ to$ 6)-$ beta$-glucan. Structural comparison of the (1 $ to$ 6)-$ beta$-glucan fraction isolated from a wild type strain and a kre1 mutant, showed that the glucan obtained from the mutant had fewer (1 $ to$ 6)-linked residues and displayed a smaller average polymer size. Therefore, the KRE1 gene product appears to be required for the stepwise synthesis of cell wall (1 $ to$ 6)-$ beta$-glucan.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.75981 |
| Date | January 1989 |
| Creators | Boone, Charles M. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 000966658, proquestno: AAINL57164, Theses scanned by UMI/ProQuest. |
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