Thermodynamics of calmodulin binding to cardiac and skeletal muscle ryanodine receptor ion channels
- Meissner, Gerhard
- Pasek, Daniel A.
- Yamaguchi, Naohiro
- Ramachandran, Srinivas
- Dokholyan, Nikolay V.
- Tripathy, Ashutosh
Publication date
January 2009
DOIAbstract
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 Ca2+ concentrations from <0.01 to 100 μM. At 0.15 μM Ca2+, [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 μM Ca2+ 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
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