Yeast sugar transporters.

Transport of sugars is a fundamental property of all eukaryotic cells. Of particular importance is the uptake of glucose, a preferred carbon and energy source. The rate of glucose utilization in yeast is often dictated by the activity and concentration of glucose transporters in the plasma membrane. Given the importance of transport as a site of control of glycolytic flux, the regulation of glucose transporters is necessarily complex. The molecular analysis of these transporters in Saccharomyces has revealed the existence of a multigene family of sugar carriers. Recent data have raised the question of the actual role of all of these proteins in sugar catabolism, as some appear to be lowly expressed, and point mutations of these genes may confer pleiotropic phenotypes, inconsistent with a simple role as catabolic transporters. The transporters themselves appear to be intimately involved in the process of sensing glucose, a model for which there is growing support.