Ryanodine receptor protein (RYR)

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The ryanodine receptor (RYR) functions as a channel for release of calcium from endoplasmic reticulum of muscle and brain. The isoforms are ~5000 residues long and contain two EF- hands, the second of which is inferred to bind calcium. The channels open in the presence of ~10-6 M Ca2+ (calcium induced calcium release) and closed at ~10-3 M Ca2+. The EF-hands have low calcium affinity and have been suggested to function in closing the channels [85].