ArticleBiochemistry2009
Residues in the H+ translocation site define the pKa for sugar binding to LacY.
Article in Biochemistry, 2009. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 34 papers.
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Who cites it
34 citing papers in PubMed, 61 citations in OpenAlex.
- Energetic and structural control of polyspecificity in a multidrug transporter.Proceedings of the National Academy of Sciences of the United States of America · 2025Article
- Structural and functional insights of AmpG in muropeptide transport and multiple β-lactam antibiotics resistance.Nature communications · 2025Article
- Structural basis of purine nucleotide inhibition of human uncoupling protein 1.Science advances · 2023Article
- Structural and Functional Adaptability of Sucrose and Lactose Permeases fromBiochemistry · 2020Article
- The proton electrochemical gradient induces a kinetic asymmetry in the symport cycle of LacY.Proceedings of the National Academy of Sciences of the United States of America · 2020Article
- It takes two to tango: The dance of the permease.The Journal of general physiology · 2019Review
- Arg302 governs the pKProceedings of the National Academy of Sciences of the United States of America · 2019Article
- Engineered occluded apo-intermediate of LacY.Proceedings of the National Academy of Sciences of the United States of America · 2018Article
- Proton-solute coupling mechanism of the maltose transporter from Saccharomyces cerevisiae.Scientific reports · 2017Article
- pKProceedings of the National Academy of Sciences of the United States of America · 2017Article
- Energy coupling mechanisms of MFS transporters.Protein science : a publication of the Protein Society · 2015Review
- Structure of LacY with an α-substituted galactoside: Connecting the binding site to the protonation site.Proceedings of the National Academy of Sciences of the United States of America · 2015Article
- A chemiosmotic mechanism of symport.Proceedings of the National Academy of Sciences of the United States of America · 2015Article
- Galactoside-binding site in LacY.Biochemistry · 2014Article
- Structure of sugar-bound LacY.Proceedings of the National Academy of Sciences of the United States of America · 2014Article
- Structure-based mechanism for Na(+)/melibiose symport by MelB.Nature communications · 2014Article
- Evolutionary mix-and-match with MFS transporters II.Proceedings of the National Academy of Sciences of the United States of America · 2013Article
- Yeast nutrient transceptors provide novel insight in the functionality of membrane transporters.Current genetics · 2013Article
- Real-time electrochemical monitoring of adenosine triphosphate in the picomolar to micromolar range using graphene-modified electrodes.Analytical chemistry · 2013Article
- Trp replacements for tightly interacting Gly-Gly pairs in LacY stabilize an outward-facing conformation.Proceedings of the National Academy of Sciences of the United States of America · 2013Article
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Authors and funding
5 authors at 2 institutions in 2 countries.
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Abstract
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 determine which residues may be responsible for this alkaline pKa. Mutations in the sugar-binding site (Glu126, Trp151, Glu269) markedly decrease affinity for sugar but do not alter the pKa for binding. In contrast, replacements for residues involved in H+ translocation (Arg302, Tyr236, His322, Asp240, Glu325, Lys319) exhibit pKa values for sugar binding that are either shifted toward neutral pH or independent of pH. Values for the apparent dissociation constant for sugar binding (K(d)(app)) increase greatly for all mutants except neutral replacements for Glu325 or Lys319, which are characterized by remarkably high affinity sugar binding (i.e., low K(d)(app)) from pH 5.5 to pH 11. The pH dependence of the on- and off-rate constants for sugar binding measured directly by stopped-flow fluorometry implicates k(off) as a major factor for the affinity change at alkaline pH and confirms the effects of pH on K(d)(app) inferred from steady-state fluorometry. These results indicate that the high pKa for sugar binding by wild-type LacY cannot be ascribed to any single amino acid residue but appears to reside within a complex of residues involved in H+ translocation. There is structural evidence for water bound in this complex, and the water could be the site of protonation responsible for the pH dependence of sugar binding.
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