The Major Facilitator Superfamily (MFS) is a large and diverse group of secondary transporters that includes uniporters, symporters, and antiporters. MFS proteins facilitate the transport across cytoplasmic or internal membranes of a variety of substrates including ions, sugar phosphates, drugs, neurotransmitters, nucleosides, amino acids, and peptides. They do so using the electrochemical potential of the transported substrates. Uniporters transport a single substrate, while symporters and antiporters transport two substrates in the same or in opposite directions, respectively, across membranes. MFS proteins are typically 400 to 600 amino acids in length, and the majority contain 12 transmembrane alpha helices (TMs) connected by hydrophilic loops. The N- and C-terminal halves of these proteins display weak similarity and may be the result of a gene duplication/fusion event. Based on kinetic studies and the structures of a few bacterial superfamily members, GlpT (glycerol-3-phosphate transporter), LacY (lactose permease), and EmrD (multidrug transporter), MFS proteins are thought to function through a single substrate binding site, alternating-access mechanism involving a rocker-switch type of movement. Bacterial members function primarily for nutrient uptake, and as drug-efflux pumps to confer antibiotic resistance. Some MFS proteins have medical significance in humans such as the glucose transporter Glut4, which is impaired in type II diabetes, and glucose-6-phosphate transporter (G6PT), which causes glycogen storage disease when mutated.
Comment:based on the structure of Escherichia coli lactose permease.
Comment:substrates bind at the substrate translocation pore, which has access to both sides of the membrane in an alternating fashion through a conformational change of the MFS.
Comment:since MFS proteins facilitate the transport of many different substrates, the residues involved in substrate binding may not be strictly conserved among superfamily members.
Structure:1PV7_A; Escherichia coli Lactose Permease binds the substrate homolog TDG; defined at 5A contacts - View structure with Cn3D
cd06174 is part of a hierarchy of related CD models. Use the graphical representation to navigate this hierarchy. cd06174 is a member of the superfamily cl17904.
cd06174 Sequence Cluster
Sub-family Hierarchy
Citing CDD
Marchler-Bauer A et al. (2013), "CDD: conserved domains and protein three-dimensional structure.", Nucleic Acids Res. 41(D1):D384-52.
Marchler-Bauer A et al. (2013), "CDD: conserved domains and protein three-dimensional structure.", Nucleic Acids Res. 41(D1):D384-52.
