The substrate-binding site in the lactose permease of Escherichia coli
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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 کاملUnraveling the mechanism of the lactose permease of Escherichia coli.
We studied the effect of pH on ligand binding in wild-type lactose permease or mutants in the four residues-Glu-269, Arg-302, His-322, and Glu-325-that are the key participants in H(+) translocation and coupling between sugar and H(+) translocation. Although wild-type permease or mutants in Glu-325 and Arg-302 exhibit marked decreases in affinity at alkaline pH, mutants in either His-322 or Glu...
متن کاملTopography of lactose permease from Escherichia coli.
The topography of lactose permease, in native membrane vesicles and after reconstitution of the purified protein into proteoliposomes, has been investigated by labeling the membrane-embedded portions of the protein using photoactivatable, hydrophobic reagents and by labeling the exposed portions of the protein with water-soluble, electrophilic reagents. Some sites of modification have been loca...
متن کاملStructure and mechanism of the lactose permease of Escherichia coli.
Membrane transport proteins that transduce free energy stored in electrochemical ion gradients into a concentration gradient are a major class of membrane proteins. We report the crystal structure at 3.5 angstroms of the Escherichia coli lactose permease, an intensively studied member of the major facilitator superfamily of transporters. The molecule is composed of N- and C-terminal domains, ea...
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ژورنال
عنوان ژورنال: Proceedings of the National Academy of Sciences
سال: 1998
ISSN: 0027-8424,1091-6490
DOI: 10.1073/pnas.95.17.9802