The Journal of General Physiology
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Published online October 27, 2008
doi:10.1085/jgp.200810013
The Journal of General Physiology, Vol. 132, No. 5, 575-585
The Rockefeller University Press, 0022-1295 $30.00
© 2008 Razumova et al.
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ARTICLE

 Contribution of the Myosin Binding Protein C Motif to Functional Effects in Permeabilized Rat Trabeculae



Maria V. Razumova, Kristina L. Bezold, An-Yue Tu, Michael Regnier, and Samantha P. Harris

Department of Bioengineering, University of Washington, Seattle, WA 98195

Correspondence to Samantha P. Harris: samharris{at}ucdavis.edu

Myosin binding protein C (MyBP-C) is a thick-filament protein that limits cross-bridge cycling rates and reduces myocyte power output. To investigate mechanisms by which MyBP-C affects contraction, we assessed effects of recombinant N-terminal domains of cardiac MyBP-C (cMyBP-C) on contractile properties of permeabilized rat cardiac trabeculae. Here, we show that N-terminal fragments of cMyBP-C that contained the first three immunoglobulin domains of cMyBP-C (i.e., C0, C1, and C2) plus the unique linker sequence termed the MyBP-C "motif" or "m-domain" increased Ca2+ sensitivity of tension and increased rates of tension redevelopment (i.e., ktr) at submaximal levels of Ca2+. At concentrations ≥20 µM, recombinant proteins also activated force in the absence of Ca2+ and inhibited maximum Ca2+-activated force. Recombinant proteins that lacked the combination of C1 and the motif did not affect contractile properties. These results suggest that the C1 domain plus the motif constitute a functional unit of MyBP-C that can activate the thin filament.

K.L. Bezold and S.P. Harris' present address is Dept. of Neurobiology, Physiology, and Behavior, University of California, Davis, Davis, CA 95616.

Abbreviations used in this paper: cMyBP-C, cardiac myosin binding protein C; MyBP-C, myosin binding protein C.

© 2008 Razumova et al. This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.jgp.org/misc/terms.shtml). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 3.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/3.0/).


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J. F. Shaffer, R. W. Kensler, and S. P. Harris
The Myosin-binding Protein C Motif Binds to F-actin in a Phosphorylation-sensitive Manner
J. Biol. Chem., May 1, 2009; 284(18): 12318 - 12327.
[Abstract] [Full Text] [PDF]


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