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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:dateCreated |
1988-7-14
|
| pubmed:abstractText |
Present evidence demonstrates that the Na-K pump rate is voltage dependent, whereas early work was largely inconclusive. The I-V relationship has a positive slope over a wide voltage range, and the existence of a negative slope region is now doubtful. Monotonic voltage dependence is consistent with the reaction cycle containing a single voltage-dependent step. Recent measurements suggest that this voltage-dependent step occurs during Na translocation and may be deocclusion of Na+. In addition, two results suggest that K translocation is voltage insensitive: (a) large positive potentials appear to have no influence on Rb-Rb exchange or associated conformational transitions; and (b) transient currents associated with Na translocation appear to involve movement of a single charge, which is sufficient for a 3Na-2K cycle. The simplest interpretation is that the pump's cation binding sites supply two negative charges. Pre-steady-state measurements demonstrate that Na translocation precedes the pump cycle's rate-limiting step, presumably K translocation. But, because K translocation seems voltage insensitive, the voltage dependence of the steady-state pump rate probably reflects that of the concentration of the intermediate entering this slow step. Further pump current and flux data (both transient and steady-state), carefully determined over a range of conditions, should increase our understanding of the voltage-dependent step(s) in the Na-K pump cycle.
|
| pubmed:grant | |
| pubmed:language |
eng
|
| pubmed:journal | |
| pubmed:citationSubset |
IM
|
| pubmed:chemical | |
| pubmed:status |
MEDLINE
|
| pubmed:issn |
0066-4278
|
| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:volume |
50
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
225-41
|
| pubmed:dateRevised |
2007-11-14
|
| pubmed:meshHeading | |
| pubmed:year |
1988
|
| pubmed:articleTitle |
Voltage dependence of the Na-K pump.
|
| pubmed:affiliation |
Department of Cell Biology and Physiology, Washington University, School of Medicine, St. Louis, Missouri 63110.
|
| pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, P.H.S.,
Review,
Research Support, Non-U.S. Gov't
|