title: Reduced cross-bridge dependent stiffness of skinned myocardium from mice lacking cardiac myosin binding protein-C.
abstract: The role of cardiac myosin binding protein-C (MyBP-C) on myocardial stiffness was examined in skinned papillary muscles of wild-type (WT(+/+)) and homozygous truncated cardiac MyBP-C (MyBP-C(t/t)) male mice. No MyBP-C was detected by gel electrophoresis or by Western blots in the MyBP-C(t/t) myocardium. Rigor-bridge dependent myofilament stiffness, i.e., rigor minus relaxed stiffness, in the MyBP-C(t/t) myocardium (281 ± 44 kN/m(2)) was 44% that in WT(+/+) (633 ± 141 kN/m(2)). The center-to-center spacing between thick filaments as determined by X-ray diffraction in MyBP-C(t/t) (45.0 ± 1.2 nm) was not significantly different from that in WT(+/+) (43.2 ± 0.9 nm). The fraction of cross-sectional area comprised of myofibrils, as determined by electron microscopy, was reduced in the MyBP-C(t/t) (39.9%) by 10% compared to WT(+/+) (44.5%). These data suggest that the 56% reduction in rigor-bridge dependent stiffness of the skinned MyBP-C(t/t) myocardium could not be due solely to a 10% reduction in the number of thick filaments per cross-sectional area and must also be due to approximately 50% reduction in the stiffness of the rigor-bridge attached thick filaments lacking MyBP-C. (Mol Cell Biochem 263: 73-80, 2004).
authors: Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT, 05405, USA.
authors: Bradley M
authors: BM
authors: Palmer
authors: Department of Genetics, Howard Hughes Medical Institute and Harvard Medical School, Boston, MA, 02115, USA.
authors: Bradley K
authors: BK
authors: McConnell
authors: Department of Genetics, Howard Hughes Medical Institute and Harvard Medical School, Boston, MA, 02115, USA.
authors: Guo Hua
authors: GH
authors: Li
authors: Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT, 05405, USA.
authors: Christine E
authors: CE
authors: Seidman
authors: Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT, 05405, USA.
authors: J G
authors: JG
authors: Seidman
authors: Center for Synchrotron Radiation Research and Instrumentation and Department of Biological, Chemical, and Physical Sciences, Illinois Institute of Technology, Chicago, IL, 60616, USA.
authors: Thomas C
authors: TC
authors: Irving
authors: Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT, 05405, USA.
authors: Norman R
authors: NR
authors: Alpert
authors: Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT, 05405, USA.
authors: David W
authors: DW
authors: Maughan
keywords: C-protein; compliance; homozygous; isometric tension; truncated protein