Cooperative regulation of myosin-actin interactions by a continuous flexible chain I: actin-tropomyosin systems

Smith, D.A. and Maytum, Robin and Geeves, Michael A. (2003) Cooperative regulation of myosin-actin interactions by a continuous flexible chain I: actin-tropomyosin systems. Biophysical Journal, 84 (5). pp. 3155-3167. ISSN 0006-3495 . (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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We present a model for cooperative myosin binding to the regulated actin filament, where tropomyosins are treated as a weakly-confined continuous flexible chain covering myosin binding sites. Thermal fluctuations in chain orientation are initially required for myosin binding, leaving kinked regions under which subsequent myosins may bind without further distortion of the chain. Statistical mechanics predicts the fraction of sites with bound myosin-S1 as a function of their affinities. Published S1 binding curves to regulated filaments with different tropomyosin isoforms are fitted by varying the binding constant, chain persistence length nu (in actin monomers), and chain kink energy A from a single bound S1. With skeletal tropomyosin, we find an S1 actin-binding constant of 2.2 x 10(7) M(-1), A = 1.6 k(B)T and nu = 2.7. Similar persistence lengths are found with yeast tropomyosin. Larger values are found for tropomyosin-troponin in the presence of calcium (nu = 3.7) and tropomyosins from smooth muscle and fibroblasts (nu = 4.5). The relationship of these results to structural information and the rigid-unit model of McKillop and Geeves is discussed.

Item Type: Article
Additional information: 0006-3495 (Print) Evaluation Studies Journal Article Validation Studies
Uncontrolled keywords: Actins/*chemistry/*physiology Binding Sites Comparative Study Computer Simulation Feedback Homeostasis Macromolecular Substances *Models, Biological Models, Chemical Models, Molecular Molecular Motors/chemistry/physiology Motion Muscle Contraction/physiology Myosins/*chemistry/*physiology Protein Binding Protein Conformation Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, P.H.S. Tropomyosin/*chemistry/*physiology
Subjects: Q Science
Divisions: Faculties > Science Technology and Medical Studies > School of Biosciences
Depositing User: Michael Geeves
Date Deposited: 14 Mar 2009 16:34
Last Modified: 15 Jul 2014 08:40
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