Yeast KRE genes provide evidence for a pathway of cell wall beta-glucan assembly.

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Abstract
The Saccharomyces cerevisiae KRE1 gene encodes a Ser/Thr-rich protein, that is directed into the yeast secretory pathway, where it is highly modified, probably through addition of O-linked mannose residues. Gene disruption of the KRE1 locus leads to a 40% reduced level of cell wall (1 .fwdarw. 6)-.beta.-glucan. Structural analysis of the (1 .fwdarw. 6)-.beta.-glucan fraction, isolated from a strain with a kre1 disruption mutation, showed that it had an altered structure with a smaller average polymer size. Mutations in two other loci, KRE5, and KRE6 also lead to a defect in cell wall (1 .fwdarw. 6)-.beta.-glucan production and appear to be epistatic to KRE1. These findings outline a possible pathway of assembly of yeast cell wall (1 .fwdarw. 6)-.beta.-glucan.