title: 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.
abstract: 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.
authors: Molecular Physiology & Biophysics, University of Vermont, Burlington, VT 05405, USA.
authors: Abbey
authors: A
authors: Weith
authors: Sakthivel
authors: S
authors: Sadayappan
authors: James
authors: J
authors: Gulick
authors: Michael J
authors: MJ
authors: Previs
authors: Peter
authors: P
authors: Vanburen
authors: Jeffrey
authors: J
authors: Robbins
authors: David M
authors: DM
authors: Warshaw
mesh_terms: D000199:Actins / Q000378:metabolism*; D000205:Actomyosin / Q000378:metabolism*; D020816:Amino Acid Motifs; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D002645:Chickens; D051379:Mice; D010766:Phosphorylation; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary; D000099163:Myosin Binding Protein C
chemical_list: D000199:Actins; D000205:Actomyosin; D002352:Carrier Proteins; D000099163:Myosin Binding Protein C