InterPro domain: IPR044777

This subfamily includes solute carrier family 17 member 9 (SLC17A9) and similar proteins including plant inorganic phosphate transporters (PHT4) that are also probably anion transporters. SLC17A9, also called vesicular nucleotide transporter (VNUT), is involved in vesicular storage and exocytosis of ATP. It facilitates the accumulation of ATP and other nucleotides in secretory vesicles such as adrenal chromaffin granules and synaptic vesicles [ 1 ]. It also functions as a lysosomal ATP transporter and regulates cell viability [ 2 ]. Plant PHT4 family transporters mediate the transport of inorganic phosphate and may also transport organic anions. The Arabidopsis protein AtPHT4;4 is a chloroplast-localized ascorbate transporter [ 3 ]. PHT4 proteins show differential expression that suggests specialized functions [ 4 ].

The SLC17A9-like subfamily belongs to the Solute carrier 17 (SLC17) family of the Major Facilitator Superfamily (MFS) of membrane transport proteins. MFS proteins are thought to function through a single substrate binding site, alternating-access mechanism involving a rocker-switch type of movement [ 5 ].

1. Role of vesicular nucleotide transporter VNUT (SLC17A9) in release of ATP from AR42J cells and mouse pancreatic acinar cells. Purinergic Signal 10, 431-40
2. SLC17A9 protein functions as a lysosomal ATP transporter and regulates cell viability. J Biol Chem 289, 23189-99
3. AtPHT4;4 is a chloroplast-localized ascorbate transporter in Arabidopsis. Nat Commun 6, 5928
4. Functional analysis of the Arabidopsis PHT4 family of intracellular phosphate transporters. New Phytol 177, 889-98
5. Understanding transport by the major facilitator superfamily (MFS): structures pave the way. Nat Rev Mol Cell Biol 17, 123-32