Keeping It Simple, Transport Mechanism and pH Regulation in Na+/H+ Exchangers

Călinescu, Octavian; Kühlbrandt, Werner; Fendler, Klaus

doi:10.1074/jbc.m113.542993

Cited by 43 publications

(72 citation statements)

References 22 publications

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“…For an electroneutral exchanger like MjNhaP1, an electrogenic reaction is, in theory, not required. However, the study on MjNhaP1 revealed that this exchanger, although overall electroneutral, has at least two electrogenic transport steps, which we assigned to the translocation of the Na + and H + substrate ions across the membrane (7). This enabled us to monitor the activity of the transporter by solid-supported membrane (SSM)-based electrophysiology, an experimental technique that is particularly appropriate for the characterization of prokaryotic membrane transporters (9).…”

Section: Introductionmentioning

confidence: 97%

“…In a recent study we demonstrated that the competition-based transport mechanism first proposed for the electrogenic CPA2 antiporter NhaA (EcNhaA) from Escherichia coli (6) also applies to the electroneutral CPA1 antiporter MjNhaP1 (7). Members of the CPA1 and CPA2 families share similarities in the 6-helix bundle that are essential for transport (4).…”

Section: Introductionmentioning

confidence: 99%

“…However, a major difference between members of the two subfamilies is the presence of a conserved Asn-Asp motif in the binding site of the CPA1 exchangers, whereas CPA2 exchangers have a conserved Asp-Asp motif in the same position (4, 5). The additional negatively charged Asp residue in CPA2 is proposed to be responsible for the extra H + that is transported by these exchangers compared with CPA1 (6, 7). …”

Section: Introductionmentioning

confidence: 99%

“…The striking feature of the model, in which H + and Na + ions compete for a common binding site, is that it is self-regulatory, ensuring that transport activity is switched off at extreme pH values to prevent excessive acidification or alkalinization of the cytoplasm (7, 8). For an electrogenic antiporter such as EcNhaA, at least one electrogenic reaction is required per transport cycle.…”

Section: Introductionmentioning

confidence: 99%

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Electrogenic Cation Binding in the Electroneutral Na+/H+ Antiporter of Pyrococcus abyssi

Călinescu

Linder

Wöhlert

et al. 2016

Journal of Biological Chemistry

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Na+/H+ antiporters in the CPA1 branch of the cation proton antiporter family drive the electroneutral exchange of H+ against Na+ ions and ensure pH homeostasis in eukaryotic and prokaryotic organisms. Although their transport cycle is overall electroneutral, specific partial reactions are electrogenic. Here, we present an electrophysiological study of the PaNhaP Na+/H+ antiporter from Pyrococcus abyssi reconstituted into liposomes. Positive transient currents were recorded upon addition of Na+ to PaNhaP proteoliposomes, indicating a reaction where positive charge is rapidly displaced into the proteoliposomes with a rate constant of k >200 s−1. We attribute the recorded currents to an electrogenic reaction that includes Na+ binding and possibly occlusion. Subsequently, positive charge is transported out of the cell associated with H+ binding, so that the overall reaction is electroneutral. We show that the differences in pH profile and Na+ affinity of PaNhaP and the related MjNhaP1 from Methanocaldococcus jannaschii can be attributed to an additional negatively charged glutamate residue in PaNhaP. The results are discussed in the context of the physiological function of PaNhaP and other microbial Na+/H+ exchangers. We propose that both, electroneutral and electrogenic Na+/H+ antiporters, represent a carefully tuned self-regulatory system, which drives the cytoplasmic pH back to neutral after any deviation.

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Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Electrogenic Cation Binding in the Electroneutral Na+/H+ Antiporter of Pyrococcus abyssi

Călinescu

Linder

Wöhlert

et al. 2016

Journal of Biological Chemistry

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“…We note that this model is based essentially on direct competition between the Na + ions and the protons, where protonation of D163 and D164 results in Na + repulsion, and deprotonation results in Na + attraction. Competition between substrates has been suggested and shown biochemically for NhaA (9,37).…”

Section: /Hmentioning

confidence: 99%

Simulating the function of sodium/proton antiporters

Alhadeff

Warshel

2015

Proc. Natl. Acad. Sci. U.S.A.

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The molecular basis of the function of transporters is a problem of significant importance, and the emerging structural information has not yet been converted to a full understanding of the corresponding function. This work explores the molecular origin of the function of the bacterial Na + /H + antiporter NhaA by evaluating the energetics of the Na + and H + movement and then using the resulting landscape in Monte Carlo simulations that examine two transport models and explore which model can reproduce the relevant experimental results. The simulations reproduce the observed transport features by a relatively simple model that relates the protein structure to its transporting function. Focusing on the two key aspartic acid residues of NhaA, D163 and D164, shows that the fully charged state acts as an Na + trap and that the fully protonated one poses an energetic barrier that blocks the transport of Na + . By alternating between the former and latter states, mediated by the partially protonated protein, protons, and Na + can be exchanged across the membrane at 2:1 stoichiometry. Our study provides a numerical validation of the need of large conformational changes for effective transport. Furthermore, we also yield a reasonable explanation for the observation that some mammalian transporters have 1:1 stoichiometry. The present coarse-grained model can provide a general way for exploring the function of transporters on a molecular level.transport | computational biology | membrane protein

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Structure and function of yeast and fungal Na⁺/H⁺ antiporters

Dutta

Fliegel

2017

IUBMB Life

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Sodium proton antiporters (or sodium proton exchangers [NHEs]) are a critical family of membrane proteins that exchange sodium for protons across cell membranes. In yeast and plants, their primary function is to keep the sodium concentration low inside the cytoplasm. One class of NHE constitutively expressed in yeast is the plasma membrane Na 1 /H 1 antiporter, and another class is expressed on the endosomal/ vacuolar membrane. At present, four bacterial plasma membrane antiporter structures are known and nuclear magnetic resonance structures are available for the membrane spanning transmembrane helices of mammalian and yeast NHEs.Additionally, a vast amount of mutational data are available on the role of individual amino acids and critical motifs involved in transport. We combine this information to obtain a more detailed picture of the yeast NHE plasma membrane protein and review mechanisms of transport, conserved motifs, unique residues important in function, and regulation of these proteins. The Na

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Keeping It Simple, Transport Mechanism and pH Regulation in Na+/H+ Exchangers

Cited by 43 publications

References 22 publications

Electrogenic Cation Binding in the Electroneutral Na+/H+ Antiporter of Pyrococcus abyssi

Electrogenic Cation Binding in the Electroneutral Na+/H+ Antiporter of Pyrococcus abyssi

Simulating the function of sodium/proton antiporters

Structure and function of yeast and fungal Na⁺/H⁺ antiporters

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Keeping It Simple, Transport Mechanism and pH Regulation in Na+/H+ Exchangers

Cited by 43 publications

References 22 publications

Electrogenic Cation Binding in the Electroneutral Na+/H+ Antiporter of Pyrococcus abyssi

Electrogenic Cation Binding in the Electroneutral Na+/H+ Antiporter of Pyrococcus abyssi

Simulating the function of sodium/proton antiporters

Structure and function of yeast and fungal Na+/H+ antiporters

Contact Info

Product

Resources

About

Structure and function of yeast and fungal Na⁺/H⁺ antiporters