Abstract
The Na+/K+-ATPase exports 3Na+ and imports 2K+ at the expense of the hydrolysis of 1 ATP. In the absence of K+, it carries on electroneutral, Na+-dependent transient charge movement (also known as "electroneutral Na+/Na + exchange mode") and produces a transient current containing faster and slower components in response to a sudden voltage step. Components with different speeds represent sequential release of Na+ ions from three binding sites. The effect of holding potential on slow charge movement was studied in the presence of different concentrations of ADPi, Na i+ and Nao+ with the intention of improving our understanding of Nai+ binding. However, the manipulation of [ADP]i and [Na+]i did not cause as pronounced changes as predicted in the magnitude of charge movement (Q tot), which indicated that our experimental conditions were not able to backwardly drive reaction across the energy barrier to Nai + release/rebinding steps. On the contrary, lowering [Na +]o caused evident dependence of Qtot on holding potential, with characteristics suggesting that pumps were escaping from E2P through the uncoupled Na+ efflux activity.
Original language | English (US) |
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Pages (from-to) | 203-214 |
Number of pages | 12 |
Journal | Journal of Membrane Biology |
Volume | 236 |
Issue number | 2 |
DOIs | |
State | Published - Jul 2010 |
Externally published | Yes |
Keywords
- Biophysics
- Electrophysiology
- Sodium pump
- Voltage-clamp study
ASJC Scopus subject areas
- Biophysics
- Physiology
- Cell Biology