Calcium binding to calmodulin leads to an N-terminal shift in its binding site on the ryanodine Receptor

J Biol Chem. 2001 Jan 19;276(3):2069-74. doi: 10.1074/jbc.M008891200. Epub 2000 Oct 16.


The skeletal muscle calcium release channel, ryanodine receptor, is activated by calcium-free calmodulin and inhibited by calcium-bound calmodulin. Previous biochemical studies from our laboratory have shown that calcium-free calmodulin and calcium bound calmodulin protect sites at amino acids 3630 and 3637 from trypsin cleavage (Moore, C. P., Rodney, G., Zhang, J. Z., Santacruz-Toloza, L., Strasburg, G., and Hamilton, S. L. (1999) Biochemistry 38, 8532-8537). We now demonstrate that both calcium-free calmodulin and calcium-bound calmodulin bind with nanomolar affinity to a synthetic peptide matching amino acids 3614-3643 of the ryanodine receptor. Deletion of the last nine amino acids (3635-3643) destroys the ability of the peptide to bind calcium-free calmodulin, but not calcium-bound calmodulin. We propose a novel mechanism for calmodulin's interaction with a target protein. Our data suggest that the binding sites for calcium-free calmodulin and calcium-bound calmodulin are overlapping and, when calcium binds to calmodulin, the calmodulin molecule shifts to a more N-terminal location on the ryanodine receptor converting it from an activator to an inhibitor of the channel. This region of the ryanodine receptor has previously been identified as a site of intersubunit contact, suggesting the possibility that calmodulin regulates ryanodine receptor activity by regulating subunit-subunit interactions.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Binding Sites
  • Calcium / metabolism*
  • Calmodulin / metabolism*
  • Fluorescence
  • Molecular Sequence Data
  • Protein Binding
  • Ryanodine Receptor Calcium Release Channel / chemistry
  • Ryanodine Receptor Calcium Release Channel / metabolism*
  • Tryptophan / chemistry


  • Calmodulin
  • Ryanodine Receptor Calcium Release Channel
  • Tryptophan
  • Calcium