pH- and sodium-induced changes in a sodium/proton antiporter

  • We examined substrate-induced conformational changes in MjNhaP1, an archaeal electroneutral Na+/H+-antiporter resembling the human antiporter NHE1, by electron crystallography of 2D crystals in a range of physiological pH and Na+ conditions. In the absence of sodium, changes in pH had no major effect. By contrast, changes in Na+ concentration caused a marked conformational change that was largely pH-independent. Crystallographically determined, apparent dissociation constants indicated ∼10-fold stronger Na+ binding at pH 8 than at pH 4, consistent with substrate competition for a common ion-binding site. Projection difference maps indicated helix movements by about 2 Å in the 6-helix bundle region of MjNhaP1 that is thought to contain the ion translocation site. We propose that these movements convert the antiporter from the proton-bound, outward-open state to the Na+-bound, inward-open state. Oscillation between the two states would result in rapid Na+/H+ antiport.

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Author:Cristina Paulino, Werner KühlbrandtORCiDGND
Pubmed Id:
Parent Title (English):eLife
Publisher:eLife Sciences Publications
Place of publication:Cambridge
Document Type:Article
Date of Publication (online):2014/01/28
Date of first Publication:2014/01/28
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2014/02/02
Page Number:13
Copyright Paulino and Kühlbrandt. This article is distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use and redistribution provided that the original author and source are credited.
Institutes:Biowissenschaften / Biowissenschaften
Angeschlossene und kooperierende Institutionen / MPI für Biophysik
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 57 Biowissenschaften; Biologie / 570 Biowissenschaften; Biologie
Sammlung Biologie / Sondersammelgebiets-Volltexte
Licence (German):License LogoCreative Commons - Namensnennung 3.0