SPX domain of the phosphate transporters Pho87, Pho90, Pho91, and related proteins.
This region has been named the SPX domain after (Syg1, Pho81 and XPR1). The domain is found at the amino terminus of a variety of proteins. The SPX domain of the Saccharomyces cerevisiae membrane-localized low-affinity phosphate transporters Pho87 and Pho90 auto-regulates uptake and prevents efflux. This SPX dependent inhibition is mediated by the physical interaction with Spl2. Pho91 is involved in the export of inorganic phosphate from the vacuole to the cytosol. While both, Pho87 and Pho90, transport phosphate into the cell, only Pho87 appears to also function as a sensor for high extracellular phosphate concentrations.
Jiyao W et al.(2023). "The conserved domain database in 2023.",