Dependence on pH of substrate binding to lactose carrier in Escherichia coli cytoplasmic membranes
نویسندگان
چکیده
منابع مشابه
The substrate-binding site in the lactose permease of Escherichia coli.
Site-directed N-ethylmaleimide labeling was studied with Glu-126 and/or Arg-144 mutants in lactose permease containing a single, native Cys residue at position 148 in the substrate-binding site. Replacement of either Glu-126 or Arg-144 with Ala markedly decreases Cys-148 reactivity, whereas interchanging the residues, double-Ala replacement, or replacement of Arg-144 with Lys or His does not al...
متن کاملConformational flexibility at the substrate binding site in the lactose permease of Escherichia coli.
Glu-126 (helix IV) and Arg-144 (helix V) are charge paired and play a critical role in substrate binding in the lactose permease of Escherichia coli. When Glu-126 is replaced with Asp, the permease has relatively high activity, implying that helix V has sufficient flexibility to allow Arg-144 to accommodate the decreased length of the carboxylate-containing side chain of Asp-126. Helices IV and...
متن کاملLactose carrier mutants of Escherichia coli with changes in sugar recognition (lactose versus melibiose).
The purpose of this research was to identify amino acid residues that mediate substrate recognition in the lactose carrier of Escherichia coli. The lactose carrier transports the alpha-galactoside sugar melibiose as well as the beta-galactoside sugar lactose. Mutants from cells containing the lac genes on an F factor were selected by the ability to grow on succinate in the presence of the toxic...
متن کاملLactose transport in Escherichia coli: effect of transmembrane potential difference on apparent substrate affinity.
The lac carrier of Escherichia coli enables lactose to pass across the cytoplasmic membrane and to accumulate within the cell. The energy cost of concentrative sugar uptake is borne by the transmembrane proton free-energy gradient (A&+) as envisaged by Mitchell (1977) in the form of pH and electrical potential gradients (ApH and Av). Obligate 1 : 1 proton/galactoside symport via the permease co...
متن کاملGlucose-lactose diauxie in Escherichia coli.
Growth of Escherichia coli in medium containing glucose, at a concentration insufficient to support full growth, and containing lactose, is diauxic. A mutation in the gene, CR, which determines catabolite repression specific to the lac operon, was found to relieve glucose-lactose but not glucose-maltose diauxie. Furthermore, a high concentration of lactose was shown to overcome diauxie in a CR(...
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ژورنال
عنوان ژورنال: FEBS Letters
سال: 1983
ISSN: 0014-5793
DOI: 10.1016/0014-5793(83)80352-4