Lobe-specific calmodulin binding to different ryanodine receptor isoforms.
Ryanodine receptors (RyRs) are large ion channels that are responsible for the release of Ca(2+) from the sarcoplasmic/endoplasmic reticulum. Calmodulin (CaM) is a Ca(2+) binding protein that can affect the channel open probability at both high and low Ca(2+) concentrations, shifting the Ca(2+) dependencies of channel opening in an isoform-specific manner. Here we analyze the binding of CaM and its individual domains to three different RyR regions using isothermal titration calorimetry. We compared binding to skeletal muscle (RyR1) and cardiac (RyR2) isoforms, under both Ca(2+)-loaded and Ca(2+)-free conditions. CaM can bind all three regions in both isoforms, but the binding modes differ appreciably in two segments. The results highlight a Ca(2+)/CaM and apoCaM binding site in the C-terminal fifth of the channel. This binding site is the target for malignant hyperthermia and central core disease mutations in RyR1, which affect the energetics and mode of CaM binding.
Department of Biochemistry and Molecular Biology, Life Sciences Institute, University of British Columbia , Vancouver, British Columbia V6T 1Z3, Canada.
Kelvin
K
Lau
Mandy M Y
MM
Chan
Filip
F
Van Petegem
D000818:Animals; D001665:Binding Sites; D002147:Calmodulin / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D008305:Malignant Hyperthermia / Q000235:genetics; D018482:Muscle, Skeletal / Q000378:metabolism; D009154:Mutation; D009206:Myocardium / Q000378:metabolism; D020512:Myopathy, Central Core / Q000235:genetics; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry; D011817:Rabbits; D051381:Rats; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry*; D013816:Thermodynamics
D002147:Calmodulin; D020033:Protein Isoforms; D019837:Ryanodine Receptor Calcium Release Channel