منابع مشابه
Galactoside-Binding Site in LacY
Although an X-ray crystal structure of lactose permease (LacY) has been presented with bound galactopyranoside, neither the sugar nor the residues ligating the sugar can be identified with precision at ~3.5 Å. Therefore, additional evidence is important for identifying side chains likely to be involved in binding. On the basis of a clue from site-directed alkylation suggesting that Asn272, Gly2...
متن کاملStructure of LacY with an α-substituted galactoside: Connecting the binding site to the protonation site.
The X-ray crystal structure of a conformationally constrained mutant of the Escherichia coli lactose permease (the LacY double-Trp mutant Gly-46→Trp/Gly-262→Trp) with bound p-nitrophenyl-α-d-galactopyranoside (α-NPG), a high-affinity lactose analog, is described. With the exception of Glu-126 (helix IV), side chains Trp-151 (helix V), Glu-269 (helix VIII), Arg-144 (helix V), His-322 (helix X), ...
متن کاملResidues in the H+ translocation site define the pKa for sugar binding to LacY.
A remarkably high pKa of approximately 10.5 has been determined for sugar-binding affinity to the lactose permease of Escherichia coli (LacY), indicating that, under physiological conditions, substrate binds to fully protonated LacY. We have now systematically tested site-directed replacements for the residues involved in sugar binding, as well as H+ translocation and coupling, in order to dete...
متن کاملProtonation and sugar binding to LacY.
The effect of bulk-phase pH on the apparent affinity (K(d)(app)) of purified wild-type lactose permease (LacY) for sugars was studied. K(d)(app) values were determined by ligand-induced changes in the fluorescence of either of two covalently bound fluorescent reporters positioned away from the sugar-binding site. K(d)(app) for three different galactopyranosides was determined over a pH range fr...
متن کاملRole of protons in sugar binding to LacY.
WT lactose permease of Escherichia coli (LacY) reconstituted into proteoliposomes loaded with a pH-sensitive fluorophore exhibits robust uphill H(+) translocation coupled with downhill lactose transport. However, galactoside binding by mutants defective in lactose-induced H(+) translocation is not accompanied by release of an H(+) on the interior of the proteoliposomes. Because the pK(a) value ...
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ژورنال
عنوان ژورنال: Biochemistry
سال: 2014
ISSN: 0006-2960,1520-4995
DOI: 10.1021/bi401716z