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Am J Physiol Heart Circ Physiol 290: H794-H799, 2006. First published September 30, 2005; doi:10.1152/ajpheart.00706.2005
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Role of calmodulin methionine residues in mediating productive association with cardiac ryanodine receptors

Edward M. Balog, Laura E. Norton, David D. Thomas, and Bradley R. Fruen

Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota

Submitted 28 June 2005 ; accepted in final form 23 September 2005

Calmodulin (CaM) binds to the cardiac ryanodine receptor Ca2+ release channel (RyR2) with high affinity and may act as a regulatory channel subunit. Here we determine the role of CaM Met residues in the productive association of CaM with RyR2, as assessed via determinations of [3H]ryanodine and [35S]CaM binding to cardiac muscle sarcoplasmic reticulum (SR) vesicles. Oxidation of all nine CaM Met residues abolished the productive association of CaM with RyR2. Substitution of the COOH-terminal Mets of CaM with Leu decreased the extent of CaM inhibition of cardiac SR (CSR) vesicle [3H]ryanodine binding. In contrast, replacing the NH2-terminal Met of CaM with Leu increased the concentration of CaM required to inhibit CSR [3H]ryanodine binding but did not alter the extent of inhibition. Site-specific substitution of individual CaM Met residues with Gln demonstrated that Met124 was required for both high-affinity CaM binding to RyR2 and for maximal CaM inhibition. These results thus identify a Met residue critical for the productive association of CaM with RyR2 channels.

sarcoplasmic reticulum; excitation-contraction; oxidative stress; methionine sulfoxide; ryanodine receptor Ca2+ release channel


Address for reprint requests and other correspondence: E. M. Balog, School of Applied Physiology, Georgia Institute of Technology, 281 Ferst Dr., Atlanta, GA 30332-0356 (e-mail: ed.balog{at}ap.gatech.edu)






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