5NOL

Ca2+-induced Movement of Tropomyosin on Native Cardiac Thin Filaments - "Closed" state

Experimental Data Snapshot

  • Method: ELECTRON MICROSCOPY
  • Resolution: 8.00 Å
  • Aggregation State: HELICAL ARRAY 
  • Reconstruction Method: HELICAL 

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This is version 1.2 of the entry. See complete history. 


Literature

Ca(2+)-induced movement of tropomyosin on native cardiac thin filaments revealed by cryoelectron microscopy.

Risi, C., Eisner, J., Belknap, B., Heeley, D.H., White, H.D., Schroder, G.F., Galkin, V.E.

(2017) Proc Natl Acad Sci U S A 114: 6782-6787

  • DOI: 10.1073/pnas.1700868114
  • Primary Citation of Related Structures:  
    5NOG, 5NOJ, 5NOL

  • PubMed Abstract: 

    • Muscle contraction relies on the interaction of myosin motors with F-actin, which is regulated through a translocation of tropomyosin by the troponin complex in response to Ca 2+ The current model of muscle regulation holds that at relaxing (low-Ca 2+ ) conditions tropomyosin blocks myosin binding sites on F-actin, whereas at activating (high-Ca 2+ ) conditions tropomyosin translocation only partially exposes myosin binding sites on F-actin so that binding of rigor myosin is required to fully activate the thin filament (TF) ...

    Muscle contraction relies on the interaction of myosin motors with F-actin, which is regulated through a translocation of tropomyosin by the troponin complex in response to Ca 2+ The current model of muscle regulation holds that at relaxing (low-Ca 2+ ) conditions tropomyosin blocks myosin binding sites on F-actin, whereas at activating (high-Ca 2+ ) conditions tropomyosin translocation only partially exposes myosin binding sites on F-actin so that binding of rigor myosin is required to fully activate the thin filament (TF). Here we used a single-particle approach to helical reconstruction of frozen hydrated native cardiac TFs under relaxing and activating conditions to reveal the azimuthal movement of the tropomyosin on the surface of the native cardiac TF upon Ca 2+ activation. We demonstrate that at either relaxing or activating conditions tropomyosin is not constrained in one structural state, but rather is distributed between three structural positions on the surface of the TF. We show that two of these tropomyosin positions restrain actomyosin interactions, whereas in the third position, which is significantly enhanced at high Ca 2+ , tropomyosin does not block myosin binding sites on F-actin. Our data provide a structural framework for the enhanced activation of the cardiac TF over the skeletal TF by Ca 2+ and lead to a mechanistic model for the regulation of the cardiac TF.

    Organizational Affiliation: 

    Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, VA 23507; galkinve@evms.edu.



Macromolecules
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(by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
Cardiac muscle alpha actin 1A, B, C, D, E367Sus scrofaMutation(s): 0 
Gene Names: ACTC1, ACTA1, ACTA
UniProt
Find proteins for P68137 (Sus scrofa)
Explore P68137 
Go to UniProtKB:  P68137
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP68137
Protein Feature View
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  • Reference Sequence
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Entity ID: 2
MoleculeChainsSequence LengthOrganismDetailsImage
cardiac alpha tropomyosinF, G135Sus scrofaMutation(s): 0 
Protein Feature View
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  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Method: ELECTRON MICROSCOPY
  • Resolution: 8.00 Å
  • Aggregation State: HELICAL ARRAY 
  • Reconstruction Method: HELICAL 

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2017-07-19
    Type: Initial release
  • Version 1.1: 2017-08-30
    Changes: Data collection, Refinement description
  • Version 1.2: 2018-11-21
    Changes: Advisory, Data collection, Derived calculations