Hürlimann HC Pinson B Stadler-Waibel M Zeeman SC Freimoser FM 2009 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. https://sonar.ch/global/documents/160537 eng info:eu-repo/semantics/altIdentifier/doi/10.1038/embor.2009.105 info:eu-repo/semantics/altIdentifier/pmid/19590579 EMBO reports. - 2009 Biological Transport Cyclin-Dependent Kinase Inhibitor Proteins Phosphate Transport Proteins Phosphates Protein Binding Protein Structure, Tertiary Saccharomyces cerevisiae Saccharomyces cerevisiae Proteins The SPX domain of the yeast low-affinity phosphate transporter Pho90 regulates transport activity. http://purl.org/coar/resource_type/c_6501