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Structural properties of voltage-dependent calcium channels
E W McCleskey1, M D Womack, L A Fieber
1Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110.
International Review of Cytology
|January 1, 1993
Summary
Researchers purified skeletal muscle calcium (Ca2+) channels, revealing a five-subunit structure. These channels play dual roles in muscle contraction by passing Ca2+ and triggering its release from internal stores.
Area of Science:
- Molecular Biology
- Cell Physiology
- Biophysics
Background:
- Skeletal muscle calcium channels are crucial for excitation-contraction coupling.
- Previous physiological studies suggested dual roles for these channels.
Purpose of the Study:
- To elucidate the subunit composition and structure-function relationships of skeletal muscle calcium channels.
- To investigate the roles of calcium channels in excitation-contraction coupling.
Main Methods:
- Purification of skeletal muscle calcium channels using Ca2+ channel drugs as ligands.
- Cloning of individual subunits.
- Expression studies and structure-function analyses using a Ca2+ channel-free mutant muscle.
Main Results:
- The skeletal muscle Ca2+ channel comprises a five-subunit structure: one large pore-forming protein (175 kDa) and four auxiliary subunits.
- Expression studies are advancing rapidly.
- Structure-function studies confirmed the dual role of muscle Ca2+ channels in Ca2+ passage and triggering intracellular Ca2+ release.
Conclusions:
- The five-subunit structure of the skeletal muscle Ca2+ channel has been identified.
- Muscle Ca2+ channels possess dual functions essential for excitation-contraction coupling.
- Further structure-function studies, aided by predictions and comparisons with other ion channels, are expected to accelerate progress.