The SPX domain of the yeast low-affinity phosphate transporter Pho90 regulates transport activity.
Yeast has two phosphate-uptake systems that complement each other: the high-affinity transporters (Pho84 and Pho89) are active under phosphate starvation, whereas Pho87 and Pho90 are low-affinity transporters that function when phosphate is abundant. Here, we report new regulatory functions of the amino-terminal SPX domain of Pho87 and Pho90. By studying truncated versions of Pho87 and Pho90, we show that the SPX domain limits the phosphate-uptake velocity, suppresses phosphate efflux and affects the regulation of the phosphate signal transduction pathway. Furthermore, split-ubiquitin assays and co-immunoprecipitation suggest that the SPX domain of both Pho90 and Pho87 interacts physically with the regulatory protein Spl2. This work suggests that the SPX domain inhibits low-affinity phosphate transport through a physical interaction with Spl2.
Hürlimann
Hans Caspar
HC
Institute of Plant Sciences, ETH Zurich, Universitätstrasse 2, 8092 Zurich, Switzerland.
Pinson
Benoît
B
Stadler-Waibel
Martha
M
Zeeman
Samuel C
SC
Freimoser
Florian M
FM
D001692:Biological Transport; D050756:Cyclin-Dependent Kinase Inhibitor Proteins / Q000235:genetics / Q000378:metabolism; D028061:Phosphate Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D050756:Cyclin-Dependent Kinase Inhibitor Proteins; C544652:Pho90 protein, S cerevisiae; D028061:Phosphate Transport Proteins; D010710:Phosphates; C111070:SPL2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins