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Linker-gating ring complex as passive spring and Ca(2+)-dependent machine for a voltage- and Ca(2+)-activated
Xiaowei Niu1, Xiang Qian, Karl L Magleby
1Department of Physiology and Biophysics, University of Miami School of Medicine, P.O. Box 016430, Miami, Florida 33101, USA.
Neuron
|June 9, 2004
Summary
The gating ring and linker complex in potassium (K+) channels acts like a spring, influencing channel activity. Calcium (Ca2+) binding modifies this force, affecting both voltage-dependent and Ca2+-activated gating.
Area of Science:
- Molecular biology
- Biophysics
- Ion channel function
Background:
- Ion channels control ion flow across cell membranes.
- Agonist-gated channels may use intracellular gating rings and linkers.
- The mechanical role of these components is not fully understood.
Purpose of the Study:
- To investigate the mechanical role of linkers in voltage- and Ca2+-activated K+ (BK) channels.
- To determine how linker length affects channel gating.
- To elucidate the contribution of passive and Ca2+-dependent forces to BK channel function.
Main Methods:
- Site-directed mutagenesis to alter linker lengths in BK channels.
- Electrophysiological recordings to measure channel activity.
- Analysis of channel gating kinetics and voltage dependence.
Main Results:
- Shortening BK channel linkers increased channel activity.
- Lengthening linkers decreased channel activity, irrespective of Ca2+ presence.
- A mechanical model suggests the linker-gating ring acts as a passive spring modulated by Ca2+.
Conclusions:
- Linker length is critical for modulating BK channel gating.
- The linker-gating ring complex provides a passive force influencing voltage-dependent gating.
- Calcium binding alters this force, contributing to channel activation.