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rdf:type |
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lifeskim:mentions |
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pubmed:dateCreated |
1996-10-4
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pubmed:abstractText |
1. We have studied the effects on the physiological properties of the Na(+)-K+ pump of both 31- and 40-amino acid N-terminal truncated forms of the alpha-subunit of the Na(+)-K(+)-ATPase. 2. Na(+)-K+ pumps that were moderately ouabain resistant (K1 = 50 microM) were expressed in the Xenopus oocyte by injection of wild-type or truncated variants of the Bufo marinus Na(+)-K(+)-ATPase alpha-subunit cRNA with Bufo beta-subunit cRNA. The function of the Na(+)-K+ pump was studied by electrophysiological methods after Na+ loading and inhibition of the endogenous Xenopus Na(+)-K(+)-ATPase by exposure to a low concentration (0.2 microM) of ouabain. 3. The voltage-dependent potassium activation kinetics of the Na(+)-K+ pump current and the ouabain-sensitive proton-dependent inward current were studied using the two-electrode voltage-clamp technique. A novel technique involving permeabilization of part of the oocyte membrane with digitonin was developed to enable study of the pre-steady-state current following fast voltage perturbation. 4. By comparison with the wild type, the 40-amino acid N-terminal truncation induced a lower level of Na(+)-K+ pump current, a 2- to 3-fold reduction in the apparent external K+ affinity when measured in the presence of extracellular Na+, a relative increase in the proton-dependent inward current, and a reduction in the rate constant of the pre-steady-state current following a voltage step towards a positive membrane potential. The 31-amino acid truncation induced changes that were qualitatively similar but of smaller magnitude. 5. We have analysed these results using a kinetic model of the Na(+)-K+ pump cycle and have shown that all these effects can be explained by the change in a single rate constant in the cycle kinetics, namely a reduction in the rate of the main charge translocating part of the Na(+)-K+ pump cycle, i.e. the forward E1 to E2 conformational change, the deocclusion and release of Na+ to the external side. 6. The highly charged N-terminal segment seems to be directly involved in the mechanism that translocates Na+ ions across the membrane's electrical field.
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pubmed:commentsCorrections |
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-126698,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-1309755,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-1380956,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-1382190,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-139923,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-146517,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-1652644,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-1653015,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-1653228,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-1655538,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-1717977,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-1880791,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-2430183,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-2556932,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-3017424,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-3017974,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-3041003,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-6245692,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-7525571,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-7682009,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-7807047,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-7900766,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-7929042,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-8011923,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-8035166,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-8057080,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-8074192,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-8118453,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-8380499,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-8382257,
http://linkedlifedata.com/resource/pubmed/commentcorrection/8815195-8383596
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pubmed:language |
eng
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pubmed:journal |
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pubmed:citationSubset |
IM
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pubmed:chemical |
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pubmed:status |
MEDLINE
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pubmed:month |
Mar
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pubmed:issn |
0022-3751
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pubmed:author |
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pubmed:issnType |
Print
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pubmed:day |
15
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pubmed:volume |
491 ( Pt 3)
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
579-94
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pubmed:dateRevised |
2009-11-18
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pubmed:meshHeading |
pubmed-meshheading:8815195-Amino Acid Sequence,
pubmed-meshheading:8815195-Animals,
pubmed-meshheading:8815195-Base Sequence,
pubmed-meshheading:8815195-Bufo marinus,
pubmed-meshheading:8815195-Cations,
pubmed-meshheading:8815195-Electrophysiology,
pubmed-meshheading:8815195-Enzyme Inhibitors,
pubmed-meshheading:8815195-Molecular Sequence Data,
pubmed-meshheading:8815195-Mutation,
pubmed-meshheading:8815195-Oocytes,
pubmed-meshheading:8815195-Ouabain,
pubmed-meshheading:8815195-Patch-Clamp Techniques,
pubmed-meshheading:8815195-Potassium,
pubmed-meshheading:8815195-Sodium-Potassium-Exchanging ATPase,
pubmed-meshheading:8815195-Xenopus laevis
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pubmed:year |
1996
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pubmed:articleTitle |
Role in cation translocation of the N-terminus of the alpha-subunit of the Na(+)-K+ pump of Bufo.
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pubmed:affiliation |
Institute of Pharmacology and Toxicology, University of Lausanne, Switzerland.
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pubmed:publicationType |
Journal Article,
Research Support, Non-U.S. Gov't
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