title: Cardiac myosin binding protein-C restricts intrafilament torsional dynamics of actin in a phosphorylation-dependent manner.
abstract: 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, interacting with 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 actin more tightly than the N-terminal half (C0-C4), which had smaller effects on actin dynamics that were 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.
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA. bacolson@umn.edu
authors.forename: Brett A
authors.initials: BA
authors.lastname: Colson
authors.forename: Inna N
authors.initials: IN
authors.lastname: Rybakova
authors.forename: Ewa
authors.initials: E
authors.lastname: Prochniewicz
authors.forename: Richard L
authors.initials: RL
authors.lastname: Moss
authors.forename: David D
authors.initials: DD
authors.lastname: Thomas
mesh_terms: D000199:Actins / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D055592:Biophysical Phenomena; D024722:Cardiac Myosins / Q000737:chemistry* / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005454:Fluorescence Polarization; D051379:Mice; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D009200:Myocardial Contraction / Q000502:physiology; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D054730:Protein Interaction Domains and Motifs; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000099163:Myosin Binding Protein C
chemical_list: D000199:Actins; D024722:Cardiac Myosins; D002352:Carrier Proteins; D010446:Peptide Fragments; D020033:Protein Isoforms; D011994:Recombinant Proteins; D000099163:Myosin Binding Protein C