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A voltage-activated cation transport pathway associated with the sodium pump
1Department of Cellular and Molecular Physiology, Harvard Medical School, Boston, MA 02115.
Biochimica Et Biophysica Acta
|December 9, 1991
Summary
Shark Na,K-ATPase in proteoliposomes exhibits voltage-dependent cation conductance, similar to human cells. This pathway, inhibited by oligomycin, suggests the Na-K pump interacts with its gating mechanism.
Area of Science:
- Biochemistry
- Membrane Transport
- Ion Channels
Background:
- The Na,K-ATPase (sodium-potassium adenosine triphosphatase) is crucial for maintaining cellular ion gradients.
- Understanding the ion transport mechanisms of Na,K-ATPase is vital for cellular physiology.
Purpose of the Study:
- To investigate the cation conductance activated by inside positive potentials in reconstituted shark Na,K-ATPase.
- To compare the voltage-dependence and inhibition patterns of this conductance with mammalian erythrocytes.
Main Methods:
- Reconstitution of shark Na,K-ATPase into proteoliposomes.
- Electrophysiological measurements to characterize cation conductance.
- Inhibition studies using external oligomycin.
Main Results:
- Inside positive potentials activate a cation conductance in shark Na,K-ATPase proteoliposomes.
- This conductance displays voltage-dependence similar to that observed in mammalian erythrocytes.
- External oligomycin inhibits the voltage-activated pathway by trapping the Na,K-ATPase in a Na-occluded E1 conformation.
Conclusions:
- A cation-permeable pathway, activated by inside positive potentials, is associated with the Na-K pump.
- This pathway likely involves interaction with the pump's gating mechanism.
- Findings suggest a conserved mechanism across different species for potential ion leak through the Na-K pump.