3J4K

Cryo-EM structures of the actin:tropomyosin filament reveal the mechanism for the transition from C- to M-state


Experimental Data Snapshot

  • Method: ELECTRON MICROSCOPY
  • Resolution: 8.00 Å
  • Aggregation State: FILAMENT 
  • Reconstruction Method: SINGLE PARTICLE 

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This is version 1.3 of the entry. See complete history


Literature

Cryo-EM Structures of the Actin:Tropomyosin Filament Reveal the Mechanism for the Transition from C- to M-State.

Sousa, D.R.Stagg, S.M.Stroupe, M.E.

(2013) J Mol Biol 425: 4544-4555

  • DOI: https://doi.org/10.1016/j.jmb.2013.08.020
  • Primary Citation of Related Structures:  
    3J4K

  • PubMed Abstract: 

    Tropomyosin (Tm) is a key factor in the molecular mechanisms that regulate the binding of myosin motors to actin filaments (F-Actins) in most eukaryotic cells. This regulation is achieved by the azimuthal repositioning of Tm along the actin (Ac):Tm:troponin (Tn) thin filament to block or expose myosin binding sites on Ac. In striated muscle, including involuntary cardiac muscle, Tm regulates muscle contraction by coupling Ca(2+) binding to Tn with myosin binding to the thin filament. In smooth muscle, the switch is the posttranslational modification of the myosin. Depending on the activation state of Tn and the binding state of myosin, Tm can occupy the blocked, closed, or open position on Ac. Using native cryogenic 3DEM (three-dimensional electron microscopy), we have directly resolved and visualized cardiac and gizzard muscle Tm on filamentous Ac in the position that corresponds to the closed state. From the 8-Å-resolution structure of the reconstituted Ac:Tm filament formed with gizzard-derived Tm, we discuss two possible mechanisms for the transition from closed to open state and describe the role Tm plays in blocking myosin tight binding in the closed-state position.


  • Organizational Affiliation

    Department of Biological Science and Institute of Molecular Biophysics, Florida State University, 91 Chieftan Way, Tallahassee, FL 32306, USA; Department of Physiology and Biophysics, Boston University School of Medicine, 72 East Concord Street, Boston, MA 02118-2526, USA.


Macromolecules
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Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Actin, alpha skeletal muscle
A, B, C, D, E
375Oryctolagus cuniculusMutation(s): 0 
UniProt
Find proteins for P68135 (Oryctolagus cuniculus)
Explore P68135 
Go to UniProtKB:  P68135
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP68135
Sequence Annotations
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  • Reference Sequence
Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 2
MoleculeChains Sequence LengthOrganismDetailsImage
tropomyosin
F, G
136Gallus gallusMutation(s): 0 
Sequence Annotations
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: ELECTRON MICROSCOPY
  • Resolution: 8.00 Å
  • Aggregation State: FILAMENT 
  • Reconstruction Method: SINGLE PARTICLE 
EM Software:
TaskSoftware PackageVersion
RECONSTRUCTIONEMAN
RECONSTRUCTIONMATLAB
RECONSTRUCTIONSPIDER

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2013-09-25
    Type: Initial release
  • Version 1.1: 2013-11-13
    Changes: Database references
  • Version 1.2: 2018-07-18
    Changes: Author supporting evidence, Data collection
  • Version 1.3: 2024-02-21
    Changes: Data collection, Database references, Derived calculations, Refinement description