5ijh
From Proteopedia
Structure of the SPX domain of the human phosphate transporter XPR1 in complex with a sulfate ion
Structural highlights
DiseaseS53A1_HUMAN Bilateral striopallidodentate calcinosis. The disease is caused by variants affecting the gene represented in this entry. FunctionS53A1_HUMAN Inorganic ion transporter that mediates phosphate ion export across plasma membrane. Plays a major role in phosphate homeostasis, preventing intracellular phosphate accumulation and possible calcium phosphate precipitation, ultimately preserving calcium signaling. The molecular mechanism of phosphate transport, whether electrogenic, electroneutral or coupled to other ions, remains to be elucidated (By similarity) (PubMed:23791524, PubMed:25938945, PubMed:31043717). Binds inositol hexakisphosphate (Ins6P) and similar inositol polyphosphates, such as 5-diphospho-inositol pentakisphosphate (5-InsP7), important intracellular signaling molecules involved in regulation of phosphate flux (PubMed:27080106).[UniProtKB:Q9Z0U0][1] [2] [3] [4] Publication Abstract from PubMedPhosphorus is a macronutrient taken up by cells as inorganic phosphate (Pi). How cells sense cellular Pilevels is poorly characterized. Here we report that SPX domains, which are found in eukaryotic phosphate transporters, signaling proteins and inorganic polyphosphate polymerases, provide a basic binding surface for inositol polyphosphate signaling molecules (InsPs), whose concentrations change in response to Piavailability. Substitutions of critical binding surface residues impair InsP binding in vitro, inorganic polyphosphate synthesis in yeast and Pitransport inArabidopsis In plants, InsPs trigger the association of SPX proteins with transcription factors to regulate Pistarvation responses. We propose that InsPs communicate cytosolic Pilevels to SPX domains and enable them to interact with a multitude of proteins to regulate Piuptake, transport and storage in fungi, plants and animals. Control of eukaryotic phosphate homeostasis by inositol polyphosphate sensor domains.,Wild R, Gerasimaite R, Jung JY, Truffault V, Pavlovic I, Schmidt A, Saiardi A, Jessen HJ, Poirier Y, Hothorn M, Mayer A Science. 2016 Apr 14. pii: aad9858. PMID:27080106[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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