Properties of the cysteine-less Pho84 phosphate transporter of Saccharomyces cerevisiae

The derepressible Pho84 high-affinity phosphate permease of Saccharomyces c erevisiae, encoded by the PHO84 gene belongs to a family of phosphate:proto n symporters (PHS). The protein contains 12 native cysteine residues of whi ch five are predicted to be located in putative transmembrane regions III, VI, VIII, IX and X, and the remaining seven in the hydrophilic domains of t he protein. Here we report on the construction of a Pho84 transporter devoi d of cysteine residues (C-less) in which all 12 native residues were replac ed with serines using PCR mutagenesis and the functional consequences of th is. Our results clearly demonstrate that the C-less Pho84 variant is able t o support growth of yeast cells to the same extent as the wild-type Pho84 a nd is stably expressed under derepressible conditions and is fully active i n proton-coupled phosphate transport across the yeast plasma membrane. (C) 2001 Academic Press.