A conformation of Na(+)-K+ pump is permeable to proton

Details

Serval ID
serval:BIB_18C53CB90B82
Type
Article: article from journal or magazin.
Collection
Publications
Institution
Title
A conformation of Na(+)-K+ pump is permeable to proton
Journal
American Journal of Physiology
Author(s)
Wang  X., Horisberger  J. D.
ISSN
0002-9513 (Print)
Publication state
Published
Issued date
03/1995
Volume
268
Number
3 Pt 1
Pages
C590-5
Notes
Journal Article
Research Support, Non-U.S. Gov't --- Old month value: Mar
Abstract
The Na(+)-K+ pump is thought to operate through a two-conformation (E1-E2) transport cycle in which the cation binding sites are accessible only from one side at a time. Using Na(+)-loaded Xenopus oocytes in which Na(+)-K+ pumps were overexpressed by injection of cRNA of the Xenopus Na(+)-K+ pump alpha-and beta-sub units, we observed a Na(+)-K+ pump-mediated (ouabain-sensitive) inward current in the absence of other transportable cations, except H+, in the external solution. This inward current was strongly inwardly rectifying, pH dependent, and larger at acid pH. Under conditions favoring a large ouabain-sensitive inward current, we observed a ouabain-sensitive intracellular acidification, and the amplitude of the acidification was significantly related to the ouabain-sensitive current, indicating that this current was carried by protons. The reversal potential of the ouabain-sensitive current was dependent on external pH as expected for a proton-conductive pathway. We conclude that in the absence of external K+ the Na(+)-K+ pump can mediate a large inward electrogenic transport of proton. This is most easily explained by the hypothesis that the E2 conformation of the Na(+)-K+ pump with cation binding sites exposed to the outside is accessible to protons from both sides and thus provides a channellike pathway for protons.
Keywords
Animals Binding Sites Biological Transport Cations Electric Conductivity Female Gene Expression Hydrogen-Ion Concentration Na(+)-K(+)-Exchanging ATPase/*chemistry/genetics/*physiology Oocytes/metabolism Ouabain/pharmacology Protein Conformation *Protons Xenopus laevis
Pubmed
Web of science
Create date
24/01/2008 12:38
Last modification date
20/08/2019 12:49
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