Voltage dependence of the Na-K pump
P De Weer1, D C Gadsby, R F Rakowski
1Department of Cell Biology and Physiology, Washington University, School of Medicine, St. Louis, Missouri 63110.
Annual Review of Physiology
|January 1, 1988
Summary
The sodium-potassium pump
Area of Science:
- Biochemistry
- Cellular Physiology
- Membrane Transport
Background:
- The sodium-potassium pump (Na-K pump) is crucial for maintaining cell membrane potential.
- Previous research on the Na-K pump's voltage dependence yielded inconclusive results.
- Understanding the voltage dependence is key to elucidating the pump's mechanism.
Purpose of the Study:
- To clarify the voltage dependence of the Na-K pump's rate.
- To identify the specific step(s) in the pump cycle affected by voltage.
- To reconcile existing data on Na-K pump kinetics and voltage sensitivity.
Main Methods:
- Analysis of current-voltage (I-V) relationships for the Na-K pump.
- Investigation of ion translocation steps (Na+ and K+) using electrophysiological techniques.
- Examination of pump-associated conformational changes and transient currents.
Main Results:
- The Na-K pump rate exhibits voltage dependence, with a monotonic positive slope in the I-V relationship.
- Evidence suggests the voltage-dependent step occurs during sodium (Na+) translocation, possibly deocclusion.
- Potassium (K+) translocation and associated conformational changes appear voltage-insensitive.
Conclusions:
- The Na-K pump cycle likely involves a single voltage-dependent step during Na+ translocation.
- Voltage sensitivity of the steady-state pump rate is attributed to the concentration of an intermediate preceding the rate-limiting K+ translocation.
- Further detailed studies on pump current and flux are needed to fully understand voltage-dependent steps.
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