title: TrkH and its homolog, TrkG, determine the specificity and kinetics of cation transport by the Trk system of Escherichia coli.
abstract: The corrected sequence of the trkH gene of Escherichia coli predicts that the TrkH protein is a hydrophobic membrane protein of 483 amino acid residues, of which 41% are identical to those of the homologous and functionally analogous TrkG protein. These two proteins form the transmembrane component of the Trk system for the uptake of K+. Each protein alone is sufficient for high-level Trk activity. When Trk is assembled with the TrkG protein, Rb+ and K+ are transported with a Km near or below 1 mM; however, the Vmax for Rb+ is only about 7% of that for K+. When Trk is formed with TrkH, the affinities for both for K+ and Rb+ are somewhat lower, and the Vmax for Rb+ is only 1% of that for K+ transport. The kinetics of transport in strains with wild-type alleles at trkG and at trkH suggest that both products participate in transport.
authors.affiliation: Fachbereich Mikrobiologie, Universität Osnabrück, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Schlösser
authors.forename: M
authors.initials: M
authors.lastname: Meldorf
authors.forename: S
authors.initials: S
authors.lastname: Stumpe
authors.forename: E P
authors.initials: EP
authors.lastname: Bakker
authors.forename: W
authors.initials: W
authors.lastname: Epstein
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D017136:Ion Transport; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D011188:Potassium / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; C068653:TrkG protein, E coli; D011188:Potassium