|PROSITE documentation PDOC50850|
Transporters can be grouped in two classes, primary and secondary carriers. The primary active transporters drive solute accumulation or extrusion by using ATP hydrolysis, photon absorption, electron flow, substrate decarboxylation or methyl transfer. If charged molecules are unidirectionally pumped as a consequence of the consumption of a primary cellular energy source, electron chemical potential results. This potential can than be used to drive the active transport of additional solutes via secondary carriers.
Among the different transporter the two largest families that occur ubiquitously in all classifications of organisms are the ATP-Binding Cassette (ABC) primary transporter superfamily (see <PDOC00185>) and the Major Facilitator Superfamily (MFS). The MFS transporters are single-polypeptide secondary carriers capable only of transporting small solutes in response to chemiosmotic ion gradients [1,2]. They function as uniporters, symporters or antiporters. In addition their solute specificity are also diverse. MFS proteins contain 12 transmembrane regions (with some variations).
The 3D-structure of human GLUT1, an archetype of the major facilitator superfamily has been solved (see <PDB:1JA5>) . Helices 1-5, 8, 10-12 are arranged in a 9-member barrel-like manner, delimiting a hydrophilic central channel. Helix 7 is located in the center of the channel suggesting a role in regulating transport of solutes through the channel.
Some proteins known to belong to the MFS superfamily are listed below:
The profile we developed covers the 12 transmembrane regions.Last update:
June 2003 / First entry.
PROSITE method (with tools and information) covered by this documentation:
|1||Authors||Pao S.S. Paulsen I.T. Saier M.H. Jr.|
|Title||Major facilitator superfamily.|
|Source||Microbiol. Mol. Biol. Rev. 62:1-34(1998).|
|2||Authors||Walmsley A.R. Barrett M.P. Bringaud F. Gould G.W.|
|Title||Sugar transporters from bacteria, parasites and mammals: structure-activity relationships.|
|Source||Trends Biochem. Sci. 23:476-481(1998).|
|3||Authors||Zuniga F.A. Shi G. Haller J.F. Rubashkin A. Flynn D.R. Iserovich P. Fischbarg J.|
|Title||A three-dimensional model of the human facilitative glucose transporter Glut1.|
|Source||J. Biol. Chem. 276:44970-44975(2001).|
|4||Authors||Van Veen H.W.|
|Source||Semin. Cell Dev. Biol. 12:239-245(2001).|
|5||Authors||Harwood C.S. Nichols N.N. Kim M.K. Ditty J.L. Parales R.E.|
|Title||Identification of the pcaRKF gene cluster from Pseudomonas putida: involvement in chemotaxis, biodegradation, and transport of 4-hydroxybenzoate.|
|Source||J. Bacteriol. 176:6479-6488(1994).|