Cardiac myosin binding protein-C restricts intrafilament torsional dynamics of actin in a phosphorylation-dependent manner

Brett A. Colson, Inna N. Rybakova, Ewa Prochniewicz, Richard L. Moss, David D. Thomas

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


We have determined the effects of myosin binding protein-C (MyBP-C) and its domains on the microsecond rotational dynamics of actin, detected by time-resolved phosphorescence anisotropy (TPA). MyBP-C is a multidomain modulator of striated muscle contraction, interactingwith myosin, titin, and possibly actin. Cardiac and slow skeletal MyBP-C are known substrates for protein kinase-A (PKA), and phosphorylation of the cardiac isoform alters contractile properties and myofilament structure. To determine the effects of MyBP-C on actin structural dynamics, we labeled actin at C374 with a phosphorescent dye and performed TPA experiments. The interaction of all three MyBP-C isoforms with actin increased the final anisotropy of the TPA decay, indicating restriction of the amplitude of actin torsional flexibility by 15-20° at saturation of the TPA effect. PKA phosphorylation of slow skeletal and cardiac MyBP-C relieved the restriction of torsional amplitude but also decreased the rate of torsional motion. In the case of fast skeletal MyBP-C, its effect on actin dynamics was unchanged by phosphorylation. The isolated C-terminal half of cardiac MyBP-C (C5-C10) had effects similar to those of the full-length protein, and it bound actinmore tightly than the N-terminal half (C0-C4), which had smaller effects on actin dynamics thatwere independent of PKA phosphorylation. We propose that these MyBP-C-induced changes in actin dynamics play a role in the functional effects of MyBP-C on the actin-myosin interaction.

Original languageEnglish (US)
Pages (from-to)20437-20442
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number50
StatePublished - Dec 11 2012


  • Contractility
  • Hypertrophic cardiomyopathy
  • Site-directed probes
  • Spectroscopy

ASJC Scopus subject areas

  • General


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