Document Detail

Combined allosteric and competitive interaction between extracellular Na(+) and K(+) during ion transport by the alpha(1), alpha(2), and alpha(3) isoforms of the Na, K-ATPase.
MedLine Citation:
PMID:  10920017     Owner:  NLM     Status:  MEDLINE    
A combined allosteric and competitive model describes the interaction between extracellular Na(+) and Rb(+) during ion transport mediated by the Na, K-ATPase. The model was developed from experiments based on (86)Rb uptake by whole cells transfected with rat isoforms of the enzyme. In the absence of Na(+), only a single transport site for extracellular Rb(+) exists. After the occupation of the Na(+)-specific allosteric site, the Rb(+) transport pocket opens to allow occupation by an additional Rb(+) and the subsequent transport of the two Rb(+) ions into the cells. Na(+) can also directly compete with Rb(+) for binding to at least one of the transport sites. While the model derived here applies to each of the three rat isoforms of the Na, K-ATPase expressed in HeLa cells, subtle differences exist among the isoforms. The alpha(3)* isoform has an increased intrinsic affinity for Rb(+) and a lower affinity for the allosteric Na(+) site than alpha(1) or alpha(2)*. The stimulation of uptake observed according to the best-fit model is due to the displacement by Rb(+) of inhibitory Na(+) bound to the transport site.
D M Balshaw; L A Millette; K Tepperman; E T Wallick
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Biophysical journal     Volume:  79     ISSN:  0006-3495     ISO Abbreviation:  Biophys. J.     Publication Date:  2000 Aug 
Date Detail:
Created Date:  2000-09-29     Completed Date:  2000-09-29     Revised Date:  2010-09-14    
Medline Journal Info:
Nlm Unique ID:  0370626     Medline TA:  Biophys J     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  853-62     Citation Subset:  IM    
Department of Pharmacology and Cell Biophysics, College of Medicine, University of Cincinnati, Cincinnati, Ohio 45267-0575 USA.
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MeSH Terms
Allosteric Regulation
Allosteric Site
Binding, Competitive
Hela Cells
Isoenzymes / chemistry,  metabolism
Models, Chemical
Potassium / metabolism*
Recombinant Proteins / chemistry,  metabolism
Rubidium / pharmacokinetics
Sodium / metabolism*
Sodium-Potassium-Exchanging ATPase / chemistry*,  metabolism*
Grant Support
Reg. No./Substance:
0/Isoenzymes; 0/Recombinant Proteins; 7440-09-7/Potassium; 7440-17-7/Rubidium; 7440-23-5/Sodium; EC ATPase

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