The muscle ryanodine receptor and its intrinsic Ca2+ channel activity.
In skeletal and cardiac muscle, contraction is initiated by the rapid release of Ca2+ ions from the intracellular membrane system, sarcoplasmic reticulum. Rapid-mixing vesicle ion flux and planar lipid bilayer-single-channel measurements have shown that Ca2+ release is mediated by a high-conductance, ligand-gated Ca2+ channel. Using the Ca2+ release-specific probe ryanodine, a 30 S protein complex composed of four polypeptides of Mr approximately 400,000 has been isolated. Reconstitution of the purified skeletal and cardiac muscle 30 S complexes into planar lipid bilayers induced single Ca2+ channel currents with conductance and gating kinetics similar to those of native Ca2+ release channels. Electron microscopy revealed structural similarity with the protein bridges ("feet") that span the transverse-tubule-sarcoplasmic reticulum junction. These results suggest that striated muscle contains an intracellular Ca2+ release channel that is identical with the ryanodine receptor and the transverse-tubule-sarcoplasmic reticulum spanning feet structures.
Lai
F A
FA
Department of Biochemistry, School of Medicine, University of North Carolina, Chapel Hill 27599-7260.
Meissner
G
G
D000818:Animals; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000502:physiology*; D009132:Muscles / Q000502:physiology*; D011950:Receptors, Cholinergic / Q000302:isolation & purification / Q000502:physiology*; D019837:Ryanodine Receptor Calcium Release Channel
D015220:Calcium Channels; D011950:Receptors, Cholinergic; D019837:Ryanodine Receptor Calcium Release Channel; D002118:Calcium