The skeletal muscle (RyR1) and cardiac muscle (RyR2) ryanodine receptor calcium release channels contain a single, conserved calmodulin (CaM) binding domain, yet are differentially regulated by CaM. Here, we report that high-affinity [ 35S]CaM binding to RyR1 is driven by favorable enthalpic and entropic contributions at Ca 2+ concentrations from <0.01 to 100 μM. At 0.15 μMCa 2+, [ 35S]CaM bound to RyR2 with decreased affinity and binding enthalpy compared with RyR1. The rates of [ 35S]CaM dissociation from RyR1 increased as the temperature was raised, whereas at 0.15 μMCa 2+ the rate from RyR2 was little affected. The results suggest major differences in the energetics of CaM binding to and dissociation from RyR1 and RyR2.
All Science Journal Classification (ASJC) codes
- Structural Biology
- Molecular Biology