The glycerol channel Fps1p mediates the uptake of arsenite and antimonite in Saccharomyces cerevisiae

The Saccharomyces cerevisiae FPS1 gene encodes a glycerol channel protein i nvolved in osmoregulation. We present evidence that Fps1p mediates influx o f the trivalent metalloids arsenite and antimonite in yeast. Deletion of FP S1 improves tolerance to arsenite and potassium antimonyl tartrate. Under h igh osmolarity conditions, when the Fps1p channel is closed, wild-type cell s show the same degree of As(III) and Sb(III) tolerance as the fps1 Delta m utant. Additional deletion of FPS1 in mutants defective in arsenite and ant imonite detoxification partially suppresses their hypersensitivity to metal loid salts. Cells expressing a constitutively open form of the Fps1p channe l are highly sensitive to both arsenite and antimonite. We also show by dir ect transport assays that arsenite uptake is mediated by Fps1p. Yeast cells appear to control the Fps1p-mediated pathway of metalloid uptake, as expre ssion of the FPS1 gene is repressed upon As(III) and Sb(III) addition. To o ur knowledge, this is the first report describing a eukaryotic uptake mecha nism for arsenite and antimonite and its involvement in metalloid tolerance .