Major Facilitator Superfamily; 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.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|.
gi 115533494  12 IVALYPIVNSIFPPIFFVPFVISQMIFGIYLYRHMPETRGR 52
Cdd:cd17357  407 VGMAFPPLQSIGGGFVFIIFAIPCALFLLYLYRYLPETKGR 447

Class 1 and Class 2 Glucose transporters (GLUTs) of the Major Facilitator Superfamily; This subfamily includes Class 1 and Class 2 glucose transporters (GLUTs) including Solute carrier family 2, facilitated glucose transporter member 1 (SLC2A1, also called glucose transporter type 1 or GLUT1), SLC2A2-5 (GLUT2-5), SLC2A7 (GLUT7), SLC2A9 (GLUT9), SLC2A11 (GLUT11), SLC2A14 (GLUT14), and similar proteins. GLUTs are a family of proteins that facilitate the transport of hexoses such as glucose and fructose. There are fourteen GLUTs found in humans; they display different substrate specificities and tissue expression. They have been categorized into three classes based on sequence similarity: Class 1 (GLUTs 1-4, 14); Class 2 (GLUTs 5, 7, 9, and 11); and Class 3 (GLUTs 6, 8, 10, 12, and HMIT). GLUTs 1-5 are the most thoroughly studied and are well-established as glucose and/or fructose transporters in various tissues and cell types. GLUT proteins are comprised of about 500 amino acid residues, possess a single N-linked oligosaccharide, and have 12 transmembrane segments. They belong to the Glucose transporter -like (GLUT-like) 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.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|.
gi 115533494  12 IVALYPIVNSIFPPIFFVPFVISQMIFGIYLYRHMPETRGR 52
Cdd:cd17357  407 VGMAFPPLQSIGGGFVFIIFAIPCALFLLYLYRYLPETKGR 447

Class 1 and Class 2 Glucose transporters (GLUTs) of the Major Facilitator Superfamily; This subfamily includes Class 1 and Class 2 glucose transporters (GLUTs) including Solute carrier family 2, facilitated glucose transporter member 1 (SLC2A1, also called glucose transporter type 1 or GLUT1), SLC2A2-5 (GLUT2-5), SLC2A7 (GLUT7), SLC2A9 (GLUT9), SLC2A11 (GLUT11), SLC2A14 (GLUT14), and similar proteins. GLUTs are a family of proteins that facilitate the transport of hexoses such as glucose and fructose. There are fourteen GLUTs found in humans; they display different substrate specificities and tissue expression. They have been categorized into three classes based on sequence similarity: Class 1 (GLUTs 1-4, 14); Class 2 (GLUTs 5, 7, 9, and 11); and Class 3 (GLUTs 6, 8, 10, 12, and HMIT). GLUTs 1-5 are the most thoroughly studied and are well-established as glucose and/or fructose transporters in various tissues and cell types. GLUT proteins are comprised of about 500 amino acid residues, possess a single N-linked oligosaccharide, and have 12 transmembrane segments. They belong to the Glucose transporter -like (GLUT-like) 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.

                         10        20        30        40
                 ....*....|....*....|....*....|....*....|.
gi 115533494  12 IVALYPIVNSIFPPIFFVPFVISQMIFGIYLYRHMPETRGR 52
Cdd:cd17357  407 VGMAFPPLQSIGGGFVFIIFAIPCALFLLYLYRYLPETKGR 447