beta-1,6-glucan synthesis in Saccharomyces cerevisiae

beta-1,6-Glucan is an essential fungal-specific component of the Saccharomy ces cerevisiae cell wall that interconnects all other wall components into a lattice. Considerable biochemical and genetic effort has been directed at the identification and characterization of the steps involved in its biosy nthesis. Structural studies show that the polymer plays a central role in w all structure, attaching mannoproteins via their glycosylphosphatidylinosit ol (GPI) glycan remnant to beta-1,9-glucan and chitin. Genetic approaches h ave identified genes that upon disruption result in beta-1,6-glucan defects of varying severity, often with reduced growth or lethality. These gene pr oducts have been localized throughout the secretory pathway and at the cell surface, suggesting a possible biosynthetic route. Current structural and genetic data have therefore allowed the development of models to predict bi osynthetic events. Based on knowledge of beta-1,3-glucan and chitin synthes is, it is likely that the bulk of beta-1,6-glucan polymer synthesis occurs at the cell surface, but requires key prior intracellular events. However, the activity of most of the identified gene products remain unknown, making it unclear to what extent and how directly they contribute to the synthesi s of this polymer. With the recent availability of new tools, reagents and methods (including genomics), the field is poised for a convergence of bioc hemical and genetic methods to identify and characterize the biochemical st eps in the synthesis of this polymer.