Abstract
The ryanodine receptor (RyR) is a high-conductance Ca$^2+$ channel
of the sarcoplasmic reticulum in muscle and of the endoplasmic reticulum
in other cells. In striated muscle fibers, RyRs are responsible for
the rapid release of Ca$^2+$ that activates contraction. Ryanodine
receptors are complex molecules, with unusually large cytoplasmic
domains containing numerous binding sites for agents that control
the state of activity of the channel-forming domain of the molecule.
Structural considerations indicate that long-range interactions between
cytoplasmic and intramembrane domains control channel function. Ryanodine
receptors are located in specialized regions of the SR, where they
are structurally and functionally associated with other intrinsic
proteins and, indirectly, also with the luminal Ca$^2+$-binding
protein calsequestrin. Activation of RyRs during the early part of
the excitation-contraction coupling cascade is initiated by the activity
of surface-membrane Ca$^2+$ channels, the dihydropyridine receptors
(DHPRs). Skeletal and cardiac muscles contain different RyR and DHPR
isoforms and both contribute to the diversity in cardiac and skeletal
excitation-contraction coupling mechanisms. The architecture of the
sarcoplasmic reticulum-surface junctions determines the types of
RyR-DHPR interactions in the two muscle types.
- 9234963
- animals,
- calcium
- channel,
- channels,
- endoplasmic
- gov't,
- heart,
- humans,
- isomerism,
- l-type,
- muscle
- muscle,
- myocardium,
- p.h.s.,
- proteins,
- receptor
- release
- research
- reticulum,
- ryanodine
- sarcoplasmic
- skeletal,
- support,
- u.s.
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