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rdf:type |
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lifeskim:mentions |
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pubmed:issue |
9
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pubmed:dateCreated |
2009-5-5
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pubmed:abstractText |
The Mg(2+) dependence of the kinetics of the phosphorylation and conformational changes of Na(+),K(+)-ATPase was investigated via the stopped-flow technique using the fluorescent label RH421. The enzyme was preequilibrated in buffer containing 130 mM NaCl to stabilize the E1(Na(+))(3) state. On mixing with ATP, a fluorescence increase was observed. Two exponential functions were necessary to fit the data. Both phases displayed an increase in their observed rate constants with increasing Mg(2+) to saturating values of 195 (+/- 6) s(-1) and 54 (+/- 8) s(-1) for the fast and slow phases, respectively. The fast phase was attributed to enzyme conversion into the E2MgP state. The slow phase was attributed to relaxation of the dephosphorylation/rephosphorylation (by ATP) equilibrium and the buildup of some enzyme in the E2Mg state. Taking into account competition from free ATP, the dissociation constant (K(d)) of Mg(2+) interaction with the E1ATP(Na(+))(3) state was estimated as 0.069 (+/- 0.010) mM. This is virtually identical to the estimated value of the K(d) of Mg(2+)-ATP interaction in solution. Within the enzyme-ATP-Mg(2+) complex, the actual K(d) for Mg(2+) binding can be attributed primarily to complexation by ATP itself, with no apparent contribution from coordination by residues of the enzyme environment in the E1 conformation.
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pubmed:commentsCorrections |
http://linkedlifedata.com/resource/pubmed/commentcorrection/19413981-10191356,
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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 |
May
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pubmed:issn |
1542-0086
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pubmed:author |
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pubmed:issnType |
Electronic
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pubmed:day |
6
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pubmed:volume |
96
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
3753-61
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pubmed:dateRevised |
2010-9-27
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pubmed:meshHeading |
pubmed-meshheading:19413981-Adenosine Triphosphate,
pubmed-meshheading:19413981-Algorithms,
pubmed-meshheading:19413981-Animals,
pubmed-meshheading:19413981-Computer Simulation,
pubmed-meshheading:19413981-Fluorescence,
pubmed-meshheading:19413981-Kinetics,
pubmed-meshheading:19413981-Magnesium,
pubmed-meshheading:19413981-Nonlinear Dynamics,
pubmed-meshheading:19413981-Phosphorylation,
pubmed-meshheading:19413981-Protein Conformation,
pubmed-meshheading:19413981-Pyridinium Compounds,
pubmed-meshheading:19413981-Sharks,
pubmed-meshheading:19413981-Sodium Chloride,
pubmed-meshheading:19413981-Sodium-Potassium-Exchanging ATPase,
pubmed-meshheading:19413981-Spectrometry, Fluorescence,
pubmed-meshheading:19413981-Styrenes
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pubmed:year |
2009
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pubmed:articleTitle |
Mechanism of Mg2+ binding in the Na+,K+-ATPase.
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pubmed:affiliation |
School of Chemistry, University of Sydney, Sydney, New South Wales, Australia.
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pubmed:publicationType |
Journal Article,
Research Support, Non-U.S. Gov't
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