The effect of holding potential on charge translocation by the Na +/K+-ATPase in the absence of potassium

Yanli Ding, Robert F. Rakowski

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

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 languageEnglish (US)
Pages (from-to)203-214
Number of pages12
JournalJournal of Membrane Biology
Volume236
Issue number2
DOIs
StatePublished - Jul 2010
Externally publishedYes

Keywords

  • Biophysics
  • Electrophysiology
  • Sodium pump
  • Voltage-clamp study

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Cell Biology

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