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Proteins. 2009 Jan;74(1):207-11. doi: 10.1002/prot.22148.

Thermodynamics of calmodulin binding to cardiac and skeletal muscle ryanodine receptor ion channels.

Author information

1
Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina 27599-7260, USA. meissner@med.unc.edu

Abstract

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 [(35)S]CaM binding to RyR1 is driven by favorable enthalpic and entropic contributions at Ca(2+) concentrations from <0.01 to 100 microM. At 0.15 microM Ca(2+), [(35)S]CaM bound to RyR2 with decreased affinity and binding enthalpy compared with RyR1. The rates of [(35)S]CaM dissociation from RyR1 increased as the temperature was raised, whereas at 0.15 microM Ca(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.

PMID:
18618700
PMCID:
PMC2605178
DOI:
10.1002/prot.22148
[Indexed for MEDLINE]
Free PMC Article

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