Myosin Isoform Determines the Conformational Dynamics and Cooperativity of Actin Filaments in the Strongly Bound Actomyosin Complex

Ewa Prochniewicz-Nakayama, Harvey F. Chin, Arnon Henn, Diane E. Hannemann, Adrian O. Olivares, David D Thomas, Enrique M. De La Cruz

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


We used transient phosphorescence anisotropy to detect the microsecond rotational dynamics of erythrosin-iodoacetamide-labeled actin strongly bound to single-headed fragments of muscle myosin subfragment 1 (S1) and non-muscle myosin V (MV). The conformational dynamics of actin filaments in solution are markedly influenced by the isoform of bound myosin. Both myosins increase the final anisotropy of actin at substoichiometric binding densities, indicating long-range, non-nearest neighbor cooperative restriction of filament rotational dynamics amplitude, but the cooperative unit is larger with MV than with muscle S1. Both myosin isoforms also cooperatively affect the actin filament rotational correlation time, but with opposite effects: muscle S1 decreases rates of intrafilament torsional motion, while binding of MV increases the rates of motion. The cooperative effects on the rates of intrafilament motions correlate with the kinetics of myosin binding to actin filaments such that MV binds more rapidly and muscle myosin binds more slowly to partially decorated filaments than to bare filaments. The two isoforms also differ in their effects on the phosphorescence lifetime of the actin-bound erythrosin iodoacetamide: while muscle S1 increases the lifetime, suggesting decreased aqueous exposure of the probe, MV does not induce a significant change. We conclude that the dynamics and structure of actin in the strongly bound actomyosin complex are determined by the isoform of the bound myosin in a manner likely to accommodate the diverse functional roles of actomyosin in muscle and non-muscle cells.

Original languageEnglish (US)
Pages (from-to)501-509
Number of pages9
JournalJournal of Molecular Biology
Issue number3
StatePublished - 2010

Bibliographical note

Funding Information:
This work was supported by grants from the National Institutes of Health to D.D.T. (AR32961, AG26160) and to E.M.D.L.C. (GM071688). E.M.D.L.C. is an American Heart Association Established Investigator (0940075N), a National Science Foundation Career Award recipient (MCB-0546353), and a Hellman Family Fellow. H.F.C. is supported by the National Institutes of Health through a predoctoral fellowship (F31 DC009143) and in part by grants from the American Heart Association (0655849T) and Yale Institute for Nanoscience and Quantum Engineering to E.M.D.L.C. We thank Octavian Cornea for assistance with preparation of the manuscript, Bengt Svensson for help with structural alignment of myosin isoforms, and Igor Negrashov for phosphorescence instrumentation and analysis software.


  • Actin
  • Allostery
  • Dynamics
  • Non-muscle myosin
  • Phosphorescence


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