Solute carrier family 17 member 9 and similar proteins of the Major Facilitator Superfamily of transporters
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. It also functions as a lysosomal ATP transporter and regulates cell viability. 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. PHT4 proteins show differential expression that suggests specialized functions. 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.
Feature 1:putative chemical substrate binding pocket [chemical binding site]
Evidence:
Comment:based on the structures of MFS transporters with bound substrates, substrate analogs, and/or inhibitors
Comment:since MFS proteins facilitate the transport of many different substrates including ions, sugar phosphates, drugs, neurotransmitters, nucleosides, amino acids, and peptides, the residues involved in substrate binding may not be strictly conserved among superfamily members
Comment:the substrate binding site or translocation pore has access to both sides of the membrane in an alternating fashion through a conformational change of the MFS transporter
Jiyao W et al.(2023). "The conserved domain database in 2023.",