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  Kinetics of charge translocation in the passive downhill uptake mode of the Na+/H+ antiporter NhaA of Escherichia coli

Zuber, D., Krause, R., Venturi, M., Padan, E., Bamberg, E., & Fendler, K. (2005). Kinetics of charge translocation in the passive downhill uptake mode of the Na+/H+ antiporter NhaA of Escherichia coli. Biochimica et Biophysica Acta, Bioenergetics, 1709(3), 240-250. doi:10.1016/j.bbabio.2005.07.009.

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 Creators:
Zuber, Dirk1, Author           
Krause, R.2, Author
Venturi, Miro3, Author           
Padan, Etana4, Author
Bamberg, Ernst1, Author           
Fendler, Klaus1, Author           
Affiliations:
1Department of Biophysical Chemistry, Max Planck Institute of Biophysics, Max Planck Society, ou_2068289              
2IonGate Biosciences GmbH, Frankfurt am Main, Germany, ou_persistent22              
3Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Max Planck Society, ou_2068290              
4Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel, ou_persistent22              

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Free keywords: NhaA; Sodium proton antiporter; Uptake mode; Proteoliposome; Solid supported membrane; Electrical
 Abstract: The Na+/H+ antiporter NhaA is the main Na+ extrusion system in E. coli. Using direct current measurements combined with a solid supported membrane (SSM), we obtained electrical data of the function of NhaA purified and reconstituted in liposomes. These measurements demonstrate NhaA's electrogenicity, its specificity for Li+ and Na+ and its pronounced pH dependence in the range pH 6.5-8.5. The mutant G338S, in contrast, presents a pH independent profile, as reported previously. A complete right-side-out orientation of the NhaA antiporter within the proteoliposomal membrane was determined using a NhaA-specific antibody based ELISA assay. This allowed for the first time the investigation of NhaA in the passive downhill uptake mode corresponding to the transport of Na+ from the periplasmic to the cytoplasmic side of the membrane. In this mode, the transporter has kinetic properties differing significantly from those of the previously investigated efflux mode. The apparent Km values were 11 mM for Na+ and 7.3 mM for Li+ at basic pH and 180 mM for Na+ and 50 mM for Li+ at neutral pH. The data demonstrate that in the passive downhill uptake mode pH regulation of the carrier affects both apparent Km as well as turnover (Vmax).

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Language(s): eng - English
 Dates: 2005-07-262005-06-032005-07-272005-08-182005-09-30
 Publication Status: Published in print
 Pages: 11
 Publishing info: -
 Table of Contents: -
 Rev. Type: Peer
 Identifiers: DOI: 10.1016/j.bbabio.2005.07.009
PMID: 16139785
 Degree: -

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Title: Biochimica et Biophysica Acta, Bioenergetics
  Abbreviation : Biochim. Biophys. Acta, Bioenerg.
Source Genre: Journal
 Creator(s):
Affiliations:
Publ. Info: Amsterdam : Elsevier
Pages: - Volume / Issue: 1709 (3) Sequence Number: - Start / End Page: 240 - 250 Identifier: ISSN: 0005-2728
CoNE: https://pure.mpg.de/cone/journals/resource/954926938702_6