Is Ca2+ effect on passive K+ transport mediated by spectrin--dependent ATPase?
Biomedica Biochimica Acta
|January 1, 1987
Summary
The spectrin-dependent ATPase (sp-ATPase) enzyme activity regulates membrane permeability to potassium (K+). Its conformation influences K+ channels, affecting ion transport across the cell membrane.
Area of Science:
- Biochemistry
- Cell Biology
- Membrane Biophysics
Background:
- Cell membrane permeability to ions like potassium (K+) is crucial for cellular function.
- Calcium ions (Ca2+) are known to influence various membrane transport processes.
- The precise molecular mechanisms linking Ca2+ to K+ permeability remain incompletely understood.
Purpose of the Study:
- To identify the specific membrane component responsible for calcium (Ca2+)-dependent potassium (K+) permeability.
- To elucidate the relationship between spectrin-dependent ATPase (sp-ATPase) activity and K+ flux.
Main Methods:
- Investigated the enzyme activity of spectrin-dependent ATPase (sp-ATPase) in relation to varying Ca2+ concentrations.
- Assessed the impact of sp-ATPase inhibitors on K+ permeability.
- Determined the Ca2+ apparent dissociation constant for sp-ATPase.
Main Results:
- sp-ATPase enzyme activity inversely correlated with membrane K+ permeability; increased activity corresponded to decreased permeability, and vice versa.
- The Ca2+ apparent dissociation constant for sp-ATPase was determined to be 6 x 10(-7) M.
- Diverse chemical inhibitors of sp-ATPase activity consistently altered K+ permeability in a reciprocal manner.
Conclusions:
- The conformation of sp-ATPase is a key determinant of membrane K+ permeability.
- sp-ATPase activity appears to modulate the gating mechanisms of potassium channels.
- This finding provides a molecular link between Ca2+ signaling and passive K+ transport.
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