The high-conductance intracellular calcium (Ca 2+ ) channel RyR2 is essential for the coupling of excitation and contraction in cardiac muscle. Among various modulators, calmodulin (CaM) regulates RyR2 in a Ca 2+ -dependent manner. Here we reveal the regulatory mechanism by which porcine RyR2 is modulated by human CaM through the structural determination of RyR2 under eight conditions ...
The high-conductance intracellular calcium (Ca 2+ ) channel RyR2 is essential for the coupling of excitation and contraction in cardiac muscle. Among various modulators, calmodulin (CaM) regulates RyR2 in a Ca 2+ -dependent manner. Here we reveal the regulatory mechanism by which porcine RyR2 is modulated by human CaM through the structural determination of RyR2 under eight conditions. Apo-CaM and Ca 2+ -CaM bind to distinct but overlapping sites in an elongated cleft formed by the handle, helical and central domains. The shift in CaM-binding sites on RyR2 is controlled by Ca 2+ binding to CaM, rather than to RyR2. Ca 2+ -CaM induces rotations and intradomain shifts of individual central domains, resulting in pore closure of the PCB95 and Ca 2+ -activated channel. By contrast, the pore of the ATP, caffeine and Ca 2+ -activated channel remains open in the presence of Ca 2+ -CaM, which suggests that Ca 2+ -CaM is one of the many competing modulators of RyR2 gating.
Organizational Affiliation:
Department of Molecular Biology, Princeton University, Princeton, NJ, USA. nyan@princeton.edu.
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