Reconstitution of the histidine periplasmic transport system in membrane vesicles. Energy coupling and interaction between the binding protein and the membrane complex.
The periplasmic histidine transport system of Salmonella typhimurium has been reconstituted in isolated right-side-out membrane vesicles. The reconstituted system is entirely dependent on both the periplasmic protein, HisJ, and the membrane-bound complex, composed of proteins HisQ, HisM, and HisP. Transport is also dependent on the presence of ascorbate and phenazine methosulfate, which provide the energy for transport. Ascorbate oxidation generates a proton-motive-force, which allows ATP synthesis. ATP (or a cogenerated molecule) appears to be the immediate energy donor. Dissipation of the proton-motive-force or reduction of the level of ATP by a variety of treatments results in inhibition of transport. Vanadate inhibits transport, indicating that ATP utilization is necessary to energize transport. The interaction between liganded HisJ and the membrane complex has been measured directly: it displays Michaelis-Menten type kinetics, with a K1/2 of approximately 65 microM. The significance of this finding in terms of transport properties of whole cells is discussed.
Prossnitz
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Department of Biochemistry, University of California, Berkeley 94720.
Gee
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Ames
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D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000502:physiology; D001692:Biological Transport; D002352:Carrier Proteins / Q000502:physiology*; D002462:Cell Membrane / Q000201:enzymology / Q000502:physiology*; D004734:Energy Metabolism; D006639:Histidine / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000502:physiology; D026901:Membrane Transport Proteins / Q000502:physiology*; D012486:Salmonella typhimurium / Q000201:enzymology / Q000502:physiology
D001426:Bacterial Proteins; D002352:Carrier Proteins; D026901:Membrane Transport Proteins; D006639:Histidine; D000255:Adenosine Triphosphate; D008274:Magnesium