Enhancement of Ca2+ release channel activity by phosphorylation of the skeletal muscle ryanodine receptor.

The Ca2+ release channel of rabbit skeletal muscle sarcoplasmic reticulum (SR) can be phosphorylated by membrane associated protein kinase(s) utilizing endogenously synthesized or exogenously added ATP. The channel protein has been enriched in non-phosphorylated and phosphorylated form from heavy SR following solubilization with CHAPS (3-[(3-cholamidopropyl)dimethylammonio-1-propane-sulfonate) and ultracentrifugation on a linear sucrose/CHAPS gradient. Reconstitution of the isolated channels into planar bilayers shows that phosphorylation enhances the open probability by increasing the sensitivity towards micromolar Ca2+ and ATP. The phosphorylation induced enhancement of the channel activity can be reversed by purified protein phosphatase 2A.