Nucleotide Pocket Thermodynamics Measured by EPR Reveal How Energy Partitioning Relates Myosin Speed to Efficiency

JOURNAL OF MOLECULAR BIOLOGY

卷:407

Article

Purcell, Thomas J.^1,2  Naber, Nariman¹  Franks-Skiba, Kathy^1,2  Dunn, Alexander R.³  Eldred, Catherine C.⁴  Berger, Christopher L.⁵  Malnasi-Csizmadia, Andras⁶  Spudich, James A.⁷  Swank, Douglas M.⁴  Pate, Edward⁸  Cooke, Roger^1,2 

[1] UCSF MC 2240, Dept Biochem & Biophys, San Francisco, CA 94158 USA

[2] Univ Calif San Francisco, Cardiovasc Res Inst, San Francisco, CA 94158 USA

[3] Stanford Univ, Dept Chem Engn, Stanford, CA 94305 USA

[4] Rensselaer Polytech Inst, Dept Biol, Troy, NY 12180 USA

[5] Univ Vermont, Dept Mol Physiol & Biophys, Coll Med, Burlington, VT 05405 USA

[6] Eotvos Lorand Univ, Dept Biochem, H-1117 Budapest, Hungary

[7] Stanford Univ, Dept Biochem, Sch Med, Stanford, CA 94305 USA

[8] Washington State Univ, Dept Math, Pullman, WA 99164 USA

关键词: myosin;    actin;    muscle;    efficiency;    EPR spectroscopy;   

DOI  :  10.1016/j.jmb.2010.11.053

来源: Elsevier

【 摘 要 】

We have used spin-labeled ADP to investigate the dynamics of the nucleotide-binding pocket in a series of myosins, which have a range of velocities. Electron paramagnetic resonance spectroscopy reveals that the pocket is in equilibrium between open and closed conformations. In the absence of actin, the closed conformation is favored. When myosin binds actin, the open conformation becomes more favored, facilitating nucleotide release. We found that faster myosins favor a more closed pocket in the actomyosin.ADP state, with smaller values of Delta H-0 and Delta S-0, even though these myosins release ADP at a faster rate. A model involving a partitioning of free energy between work-generating steps prior to rate-limiting ADP release explains both the unexpected correlation between velocity and opening of the pocket and the observation that fast myosins are less efficient than slow myosins. (C) 2011 Elsevier Ltd. All rights reserved.

【 授权许可】

Free