Sugar preferences of transporter-like sensors Snf3 and Rgt2 in Saccharomyces cerevisiae

Extracellular nutrient concentrations affect several regulatory pathways in yeast. Some pathways are initiated by signalling through nutrient sensors on the cell surface, and some non-transporting sensors have high sequence similarity to transporters. Examples are Snf3 and Rgt2, which sense sugars in yeast. It has previously been suggested that Snf3 senses lower concentrations of glucose than Rgt2, and that the functions of the two proteins are overlapping. In this study, a quantitative assay was set up to directly measure the signalling activity of Snf3 and Rgt2 at various extracellular sugar concentrations. We determined apparent affinities of the two individual sensors to putative elicitors. Different growth conditions were used to investigate the influence of intracellular ligand concentration on the sensing of extracellular ligand by Snf3.