title: Sodium and potassium requirements for active transport of glutamate by Escherichia coli K-12.
abstract: Active transport of glutamate by Escherichia coli K-12 requires both Na(+) and K(+) ions. Increasing the concentration of Na(+) in the medium results in a decrease in the K(m) of the uptake system for glutamate; the capacity is not affected. Glutamate uptake by untreated cells is not stimulated by K(+). K(+)-depleted cells show a greatly reduced capacity for glutamate uptake. Preincubation of such cells in the presence of K(+) fully restores their capacity for glutamate uptake when Na(+) ions are also present in the uptake medium. Addition of either K(+) or Na(+) alone restores glutamate uptake to only about 20% of its maximum capacity in the presence of both cations. Changes in K(+) concentration affect the capacity for glutamate uptake but have no effect on the K(m) of the glutamate transport system. Ouabain does not inhibit the (Na(+)-K(+))-stimulated glutamate uptake by intact cells or spheroplasts of E. coli K-12.
mesh_terms: D001693:Biological Transport, Active; D002247:Carbon Isotopes; D004926:Escherichia coli / Q000378:metabolism*; D005971:Glutamates / Q000378:metabolism*; D005990:Glycerol / Q000378:metabolism; D007700:Kinetics; D008715:Methionine / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology*; D012964:Sodium / Q000494:pharmacology*; D013268:Stimulation, Chemical; D013386:Succinates / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D005971:Glutamates; D013386:Succinates; D010042:Ouabain; D012964:Sodium; D008715:Methionine; D005990:Glycerol; D011188:Potassium