Differential Ca2+ sensitivity of skeletal and cardiac muscle ryanodine receptors in the presence of calmodulin

Performed cross-linking experiments that identified both RyR1 and RyR2 as predominant Calmodulin (CaM) binding proteins in skeletal and cardiac sarcoplasmic reticulum, respectively and [35S]CaM binding determination further indicated comparable CaM binding to the two isoforms in the presence of micromolar Ca2+. CaM activates RyR1 and RyR2 isoforms that may potentially contribute to differences in the Ca2+ dependence of channel activation in skeletal and cardiac muscle.