NhaA crystal structure: functional–structural insights

Padan, Etana; Kozachkov, Lena; Herz, Katia; Rimon, Abraham

doi:10.1242/jeb.026708

Cited by 71 publications

(90 citation statements)

References 86 publications

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“…There are some examples of ion transporters to support such a large conformational change from the x-ray crystallographic studies. 1) E. coli NhaA, the main Na ϩ /H ϩ antiporters, has shown the large rearrangement of the transmembrane region elicited by a pH signal perceived at the entry to the cytoplasmic funnel, and this movement permits a rapid alternating-access mechanism in the middle of the membrane at the putative ion-binding site (56). 2) Ca 2ϩ -ATPase undergoes large scale up to 50 Å thermal rearrangements involving both transmembrane and cytoplasmic domains upon the Ca 2ϩ binding (57).…”

Section: Discussionmentioning

confidence: 99%

The Membrane Subunit NuoL(ND5) Is Involved in the Indirect Proton Pumping Mechanism of Escherichia coli Complex I

Nakamaru‐Ogiso

Kao

Chen

et al. 2010

Journal of Biological Chemistry

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Section: Discussionmentioning

confidence: 99%

The Membrane Subunit NuoL(ND5) Is Involved in the Indirect Proton Pumping Mechanism of Escherichia coli Complex I

Nakamaru‐Ogiso

Kao

Chen

et al. 2010

Journal of Biological Chemistry

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“…We noted that this is similar to prevailing chemiosmotic circuits in yeast, where we observed H ϩ -driven cation extrusion by NHA2. Furthermore, whereas NHE mediates electroneutral Na ϩ /H ϩ exchange, NhaA is electrogenic, with a 2H ϩ /Na ϩ stoichiometry (10). Finally, although both NHE and NhaA antiporters are highly pH-sensitive, their regulation is in opposite directions: thus, NHE is activated by acid pH, NhaA from Escherichia coli is "acid-locked" or inactive below pH 6.5, and demonstrates an increase in rate by three orders of magnitude between pH 7 and 8.5 (11).…”

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confidence: 99%

Unconventional Chemiosmotic Coupling of NHA2, a Mammalian Na+/H+ Antiporter, to a Plasma Membrane H+ Gradient

Kondapalli

Kallay

Muszelik

et al. 2012

Journal of Biological Chemistry

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“…During Na + expulsion by alkalophilic bacteria, the hydrogen ion electrochemical potential difference ( H ) that is generated by the primary electron transport system drives secondary cation exchangers such as the Na + /2H + antiporter, NhaA (Krulwich et al, 1998;Padan et al, 2005). NhaA has been cloned, characterized, crystallized and its reaction mechanism determined (Hunte et al, 2005;Padan et al, 2005;Padan et al, 2009). In the case of caterpillar K + secretion the H is generated by a primary H + VATPase , which drives a secondary K + /2H + antiporter (Wieczorek et al, 1991).…”

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confidence: 99%

Voltage coupling of primary H+ V-ATPases to secondary Na+- or K+-dependent transporters

Harvey

2009

Journal of Experimental Biology

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SUMMARY This review provides alternatives to two well established theories regarding membrane energization by H+ V-ATPases. Firstly, we offer an alternative to the notion that the H+ V-ATPase establishes a protonmotive force (pmf) across the membrane into which it is inserted. The term pmf, which was introduced by Peter Mitchell in 1961 in his chemiosmotic hypothesis for the synthesis of ATP by H+ F-ATP synthases, has two parts, the electrical potential difference across the phosphorylating membrane, Δψ, and the pH difference between the bulk solutions on either side of the membrane, ΔpH. The ΔpH term implies three phases – a bulk fluid phase on the H+ input side, the membrane phase and a bulk fluid phase on the H+ output side. The Mitchell theory was applied to H+ V-ATPases largely by analogy with H+ F-ATP synthases operating in reverse as H+ F-ATPases. We suggest an alternative, voltage coupling model. Our model for V-ATPases is based on Douglas B. Kell's 1979 `electrodic view' of ATP synthases in which two phases are added to the Mitchell model – an unstirred layer on the input side and another one on the output side of the membrane. In addition, we replace the notion that H+ V-ATPases normally acidify the output bulk solution with the hypothesis, which we introduced in 1992, that the primary action of a H+ V-ATPase is to charge the membrane capacitance and impose a Δψ across the membrane; the translocated hydrogen ions (H+s) are retained at the outer fluid–membrane interface by electrostatic attraction to the anions that were left behind. All subsequent events, including establishing pH differences in the outside bulk solution, are secondary. Using the surface of an electrode as a model, Kell's`electrodic view' has five phases – the outer bulk fluid phase, an outer fluid–membrane interface, the membrane phase, an inner fluid–membrane interface and the inner bulk fluid phase. Light flash,H+ releasing and binding experiments and other evidence provide convincing support for Kell's electrodic view yet Mitchell's chemiosmotic theory is the one that is accepted by most bioenergetics experts today. First we discuss the interaction between H+ V-ATPase and the K+/2H+ antiporter that forms the caterpillar K+ pump, and use the Kell electrodic view to explain how the H+s at the outer fluid–membrane interface can drive two H+ from lumen to cell and one K+ from cell to lumen via the antiporter even though the pH in the bulk fluid of the lumen is highly alkaline. Exchange of outer bulk fluid K+ (or Na+) with outer interface H+ in conjunction with (K+ or Na+)/2H+ antiport, transforms the hydrogen ion electrochemical potential difference, \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\overline{{\mu}}_{\mathrm{H}}\) \end{document}, to a K+electrochemical potential difference, \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\overline{{\mu}}_{\mathrm{K}}\) \end{document} or a Na+electrochemical potential difference, \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\overline{{\mu}}_{\mathrm{Na}}\) \end{document}. The \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\overline{{\mu}}_{\mathrm{K}}\) \end{document} or \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\overline{{\mu}}_{\mathrm{Na}}\) \end{document} drives K+- or Na+-coupled nutrient amino acid transporters (NATs), such as KAAT1(K+ amino acid transporter 1), which moves Na+ and an amino acid into the cell with no H+s involved. Examples in which the voltage coupling model is used to interpret ion and amino acid transport in caterpillar and larval mosquito midgut are discussed.

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NhaA crystal structure: functional–structural insights

Cited by 71 publications

References 86 publications

The Membrane Subunit NuoL(ND5) Is Involved in the Indirect Proton Pumping Mechanism of Escherichia coli Complex I

The Membrane Subunit NuoL(ND5) Is Involved in the Indirect Proton Pumping Mechanism of Escherichia coli Complex I

Unconventional Chemiosmotic Coupling of NHA2, a Mammalian Na+/H+ Antiporter, to a Plasma Membrane H+ Gradient

Voltage coupling of primary H+ V-ATPases to secondary Na+- or K+-dependent transporters

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