Linked Life Data

12135372

Source:http://linkedlifedata.com/resource/pubmed/id/12135372

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
30
pubmed:dateCreated
2002-7-23
pubmed:abstractText
The kinetics of the E(2) --> E(1) conformational change of unphosphorylated Na(+),K(+)-ATPase from rabbit kidney and shark rectal gland were investigated via the stopped-flow technique using the fluorescent label RH421 (pH 7.4, 24 degrees C). The enzyme was pre-equilibrated in a solution containing 25 mM histidine and 0.1 mM EDTA to stabilize initially the E(2) conformation. When rabbit kidney enzyme was mixed with NaCl alone, tris ATP alone or NaCl, and tris ATP simultaneously, a fluorescence decrease was observed. The reciprocal relaxation time, 1/tau, of the fluorescent transient was found to increase with increasing NaCl concentration and reached a saturating value in the presence of 1 mM tris ATP of 54 +/- 3 s(-1) in the case of rabbit kidney enzyme. The experimental behavior could be described by a binding of Na(+) to the enzyme in the E(2) state with a dissociation constant of 31 +/- 7 mM, which induces a subsequent rate-limiting conformational change to the E(1) state. Similar behavior, but with a decreased saturating value of 1/tau, was found when NaCl was replaced by choline chloride. Analogous experiments performed with enzyme from shark rectal gland showed similar effects, but with a significantly lower amplitude of the fluorescence change and a higher saturating value of 1/tau for both the NaCl and choline chloride titrations. The results suggest that Na(+) ions or salt in general play a regulatory role, similar to that of ATP, in enhancing the rate of the rate-limiting E(2) --> E(1) conformational transition by interaction with the E(2) state.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jul
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
30
pubmed:volume
41
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
9496-507
pubmed:dateRevised
2007-11-15
pubmed:meshHeading
pubmed:year
2002
pubmed:articleTitle
Mechanism of the rate-determining step of the Na(+),K(+)-ATPase pump cycle.
pubmed:affiliation
School of Chemistry, University of Sydney, Sydney NSW 2006, Australia.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't