The structure of cell wall α-glucan from fission yeast

Morphology and structural integrity of fungal cells depend on cell wall polysaccharides. The chemical structure and, biosynthesis of two types of these. polysaccharides,, chitin and. (1-->3)-beta-glucan, have been studied extensively, whereas little is known about alpha-glucan. Here we describe the chemical structure of alpha-glucan isolated: from wild-type and mutant cell walls of the fission yeast Schizosaccharomyces pombe Wild-type alpha-glucan was found to consist of a. single population of linear glucose polymers, similar to260 residues, in length. These glucose polymers were composed of two interconnected linear chains, each consisting. of similar to120. (1-->3)-linked alpha-D-glucose residues and, some. (1-->4)-linked alpha-D-glucose. residues at the reducing end. By contrast, alpha-glucan-of an alpha-glucan synthase mutant with an aberrant cell morphology and reduced alpha-glucan levels consisted of a single chain only. We propose that alpha-glucan biosynthesis involves an. ordered I series of-events, whereby two a-glucan chains are coupled to create mature cell wall alpha-glucan. This mature, forth. of cell. wall alpha-glucan is essential for fission-yeast morphogenesis.