The random-coil 'C' fragment of the dihydropyridine receptor II-III loop can activate or inhibit native skeletal ryanodine receptors

Biochem J. 2003 Jun 1;372(Pt 2):305-16. doi: 10.1042/BJ20021763.


The actions of peptide C, corresponding to (724)Glu-Pro(760) of the II-III loop of the skeletal dihydropyridine receptor, on ryanodine receptor (RyR) channels incorporated into lipid bilayers with the native sarcoplasmic reticulum membrane show that the peptide is a high-affinity activator of native skeletal RyRs at cytoplasmic concentrations of 100 nM-10 microM. In addition, we found that peptide C inhibits RyRs in a voltage-independent manner when added for longer times or at higher concentrations (up to 150 microM). Peptide C had a random-coil structure indicating that it briefly assumes a variety of structures, some of which might activate and others which might inhibit RyRs. The results suggest that RyR activation and inhibition by peptide C arise from independent stochastic processes. A rate constant of 7.5 x 10(5) s(-1).M(-1) was obtained for activation and a lower estimate for the rate constant for inhibition of 5.9 x 10(3) s(-1).M(-1). The combined actions of peptide C and peptide A (II-III loop sequence (671)Thr-Leu(690)) showed that peptide C prevented activation but not blockage of RyRs by peptide A. We suggest that the effects of peptide C indicate functional interactions between a part of the dihydropyridine receptor and the RyR. These interactions could reflect either dynamic changes that occur during excitation-contraction coupling or interactions between the proteins at rest.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / pharmacology
  • Animals
  • Calcium Channels, L-Type / metabolism*
  • Cell Membrane / physiology
  • Circular Dichroism
  • Lipid Bilayers / metabolism*
  • Magnetic Resonance Spectroscopy
  • Membrane Potentials / physiology
  • Muscle, Skeletal / drug effects*
  • Muscle, Skeletal / metabolism
  • Peptides / pharmacology*
  • Rabbits
  • Ryanodine Receptor Calcium Release Channel / metabolism*
  • Sarcoplasmic Reticulum / physiology


  • Calcium Channels, L-Type
  • Lipid Bilayers
  • Peptides
  • Ryanodine Receptor Calcium Release Channel
  • polypeptide C
  • Adenosine Triphosphate