Unique single molecule binding of cardiac myosin binding protein-C to actin and phosphorylation-dependent inhibition of actomyosin motility requires 17 amino acids of the motif domain

J Mol Cell Cardiol. 2012 Jan;52(1):219-27. doi: 10.1016/j.yjmcc.2011.09.019. Epub 2011 Sep 25.


Cardiac myosin binding protein-C (cMyBP-C) has 11 immunoglobulin or fibronectin-like domains, C0 through C10, which bind sarcomeric proteins, including titin, myosin and actin. Using bacterial expressed mouse N-terminal fragments (C0 through C3) in an in vitro motility assay of myosin-generated actin movement and the laser trap assay to assess single molecule actin-binding capacity, we determined that the first N-terminal 17 amino acids of the cMyBP-C motif (the linker between C1 and C2) contain a strong, stereospecific actin-binding site that depends on positive charge due to a cluster of arginines. Phosphorylation of 4 serines within the motif decreases the fragments' actin-binding capacity and actomyosin inhibition. Using the laser trap assay, we observed individual cMyBP-C fragments transiently binding to a single actin filament with both short (~20 ms) and long (~300 ms) attached lifetimes, similar to that of a known actin-binding protein, α-actinin. These experiments suggest that cMyBP-C N-terminal domains containing the cMyBP-C motif tether actin filaments and provide one mechanism by which cMyBP-C modulates actomyosin motion generation, i.e. by imposing an effective viscous load within the sarcomere.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism*
  • Actomyosin / metabolism*
  • Amino Acid Motifs
  • Animals
  • Carrier Proteins / chemistry*
  • Carrier Proteins / metabolism*
  • Chickens
  • Mice
  • Phosphorylation
  • Protein Binding / drug effects
  • Protein Structure, Tertiary


  • Actins
  • Carrier Proteins
  • myosin-binding protein C
  • Actomyosin