5NOG

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


Experimental Data Snapshot

  • Method: ELECTRON MICROSCOPY
  • Resolution: 11 Å
  • Aggregation State: HELICAL ARRAY 
  • Reconstruction Method: HELICAL 

wwPDB Validation 3D Report Full Report


This is version 1.1 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:  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 Ca2+ The current model of muscle regulation holds that at relaxing (low-Ca2+) ...

    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 Ca2+ The current model of muscle regulation holds that at relaxing (low-Ca2+) conditions tropomyosin blocks myosin binding sites on F-actin, whereas at activating (high-Ca2+) 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 Ca2+ 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 Ca2+, 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 Ca2+ 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.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Cardiac muscle alpha actin 1
A, B, C, D, E
367Sus scrofaGene Names: ACTA1 (ACTA)
Find proteins for P68137 (Sus scrofa)
Go to Gene View: ACTA1
Go to UniProtKB:  P68137
Entity ID: 2
MoleculeChainsSequence LengthOrganismDetails
cardiac alpha tropomyosin
F, G
135N/AN/A
Protein Feature View is not available: No corresponding UniProt sequence found.
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
ADP
Query on ADP

Download SDF File 
Download CCD File 
A, B, C, D, E
ADENOSINE-5'-DIPHOSPHATE
C10 H15 N5 O10 P2
XTWYTFMLZFPYCI-KQYNXXCUSA-N
 Ligand Interaction
MG
Query on MG

Download SDF File 
Download CCD File 
A, B, C, D, E
MAGNESIUM ION
Mg
JLVVSXFLKOJNIY-UHFFFAOYSA-N
 Ligand Interaction
Modified Residues  2 Unique
IDChainsTypeFormula2D DiagramParent
HIC
Query on HIC
A, B, C, D, E
L-PEPTIDE LINKINGC7 H11 N3 O2HIS
UNK
Query on UNK
F, G
L-PEPTIDE LINKINGC4 H9 N O2

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Experimental Data & Validation

Experimental Data

  • Method: ELECTRON MICROSCOPY
  • Resolution: 11 Å
  • Aggregation State: HELICAL ARRAY 
  • Reconstruction Method: HELICAL 

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History & Funding Information

Deposition Data


Funding OrganizationCountryGrant Number
AHAUnited StatesAid 560851

Revision History 

  • Version 1.0: 2017-07-19
    Type: Initial release
  • Version 1.1: 2017-08-30
    Type: Data collection, Refinement description