Sodium-substrate cotransport in bacteria.
A variety of sodium-substrate cotransport systems are known in bacteria. Sodium enters the cell down an electrochemical concentration gradient. There is obligatory coupling between the entry of the ion and the entry of substrate with a stoichiometry (in the cases studied) of 1:1. Thus, the downhill movement of sodium ion into the cell leads to the accumulation of substrate within the cell. The melibiose carrier of Escherichia coli is perhaps the most carefully studied of the sodium cotransport systems in bacteria. This carrier is of special interest because it can also use protons or lithium ions for cotransport. Other sodium cotransport carriers that have been studied recently are for proline, glutamate, serine-threonine, citrate and branched chain amino acids.
Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA. thomas_wilson@hms.harvard.edu
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D000595:Amino Acid Sequence; D027322:Amino Acid Transport System X-AG; D026921:Amino Acid Transport Systems, Neutral; D000597:Amino Acids, Branched-Chain / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D019343:Citric Acid / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D029968:Escherichia coli Proteins; D050491:Glutamate Plasma Membrane Transport Proteins; D005971:Glutamates / Q000378:metabolism; D017136:Ion Transport; D008553:Melibiose / Q000378:metabolism; D008969:Molecular Sequence Data; D019897:Periplasm / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D013379:Substrate Specificity; D027981:Symporters; D013912:Threonine / Q000378:metabolism
D027322:Amino Acid Transport System X-AG; D026921:Amino Acid Transport Systems, Neutral; D000597:Amino Acids, Branched-Chain; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D050491:Glutamate Plasma Membrane Transport Proteins; D005971:Glutamates; D027981:Symporters; C060609:PutP protein, E coli; D019343:Citric Acid; D013912:Threonine; D012694:Serine; D008553:Melibiose; D012964:Sodium