ArticleProceedings of the National Academy of Sciences of the United States of America2015
A chemiosmotic mechanism of symport.
Article in Proceedings of the National Academy of Sciences of the United States of America, 2015. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 58 papers.
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Who cites it
58 citing papers in PubMed, 92 citations in OpenAlex.
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- Transcendent Aspects of Proton Channels.Annual review of physiology · 2024Review
- Lactose Permease Scrambles Phospholipids.Biology · 2023Article
- Substrate-binding guides individual melibiose permeases MelB to structurally soften and to destabilize cytoplasmic middle-loop C3.Structure (London, England : 1993) · 2023Article
- The culmination of multidrug-resistant efflux pumps vs. meager antibiotic arsenal era: Urgent need for an improved new generation of EPIs.Frontiers in microbiology · 2023Review
- General principles of secondary active transporter function.Biophysics reviews · 2022Review
- Equilibrium properties of E. coli lactose permease symport-A random-walk model approach.PloS one · 2022Article
- Antimicrobial Resistance and Inorganic Nanoparticles.International journal of molecular sciences · 2021Review
- Tracking the ATP-binding response in adenylate kinase in real time.Science advances · 2021Article
- Cooperative binding ensures the obligatory melibiose/Na+ cotransport in MelB.The Journal of general physiology · 2021Article
- The Whole Is Bigger than the Sum of Its Parts: Drug Transport in the Context of Two Membranes with Active Efflux.Chemical reviews · 2021Article
- Structures and General Transport Mechanisms by the Major Facilitator Superfamily (MFS).Chemical reviews · 2021Article
- Tracking Membrane Protein Dynamics in Real Time.The Journal of membrane biology · 2021Review
- AspThe Journal of biological chemistry · 2020Article
- Human ferroportin mediates proton-coupled active transport of iron.Blood advances · 2020Article
- Expansion of the Major Facilitator Superfamily (MFS) to include novel transporters as well as transmembrane-acting enzymes.Biochimica et biophysica acta. Biomembranes · 2020Article
- A structural framework for unidirectional transport by a bacterial ABC exporter.Proceedings of the National Academy of Sciences of the United States of America · 2020Article
- Acidification of Cytoplasm in Escherichia coli Provides a Strategy to Cope with Stress and Facilitates Development of Antibiotic Resistance.Scientific reports · 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
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1 author at 1 institution in 1 country.
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Abstract
Lactose permease (LacY), a paradigm for the largest family of membrane transport proteins, catalyzes the coupled translocation of a galactoside and an H(+) across the Escherichia coli membrane (galactoside/H(+) symport). Initial X-ray structures reveal N- and C-terminal domains, each with six largely irregular transmembrane helices surrounding an aqueous cavity open to the cytoplasm. Recently, a structure with a narrow periplasmic opening and an occluded galactoside was obtained, confirming many observations and indicating that sugar binding involves induced fit. LacY catalyzes symport by an alternating access mechanism. Experimental findings garnered over 45 y indicate the following: (i) The limiting step for lactose/H(+) symport in the absence of the H(+) electrochemical gradient (∆µ̃H+) is deprotonation, whereas in the presence of ∆µ̃H+, the limiting step is opening of apo LacY on the other side of the membrane; (ii) LacY must be protonated to bind galactoside (the pK for binding is ∼10.5); (iii) galactoside binding and dissociation, not ∆µ̃H+, are the driving forces for alternating access; (iv) galactoside binding involves induced fit, causing transition to an occluded intermediate that undergoes alternating access; (v) galactoside dissociates, releasing the energy of binding; and (vi) Arg302 comes into proximity with protonated Glu325, causing deprotonation. Accumulation of galactoside against a concentration gradient does not involve a change in Kd for sugar on either side of the membrane, but the pKa (the affinity for H(+)) decreases markedly. Thus, transport is driven chemiosmotically but, contrary to expectation, ∆µ̃H+ acts kinetically to control the rate of the process.
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