Biological Assembly 1  

 3D View: Structure | Ligand Interaction

Pseudo Symmetry: Asymmetric - C1 
Pseudo Stoichiometry: Hetero 7-mer - A5B1C1 Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Hetero 7-mer - A5B2 

Biological assembly 1 assigned by authors and generated by PISA (software)

Biological Assembly Evidence: microscopy

Macromolecule Content

• Total Structure Weight: 229.30 kDa 
• Atom Count: 15790 
• Residue Count: 2105 
• Unique protein chains: 2

5NOL

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

• DOI: 10.2210/pdb5NOL/pdb
• EMDataResource: EMD-3667

• Classification: MOTOR PROTEIN
• Organism(s): Sus scrofa
• Expression System: Sus scrofa
• Mutation(s): No 


• Deposited: 2017-04-12 Released: 2017-07-19 
• Deposition Author(s): Risi, C., Eisner, J., Belknap, B., Heeley, D.H., White, H.D., Schroeder, G.F., Galkin, V.E.

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Experimental Data Snapshot

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

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

• PubMed: 28607071 
• 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). 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.

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Organizational Affiliation: 

Department of Physiological Sciences, Eastern Virginia Medical School, Norfolk, VA 23507; [e-mail].

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
Cardiac muscle alpha actin 1	A, B, C, D, E	367	Sus scrofa	Mutation(s): 0  Gene Names: ACTC1, ACTA1, ACTA
Find proteins for P68137 (Sus scrofa) Explore P68137  Go to UniProtKB:  P68137

Entity ID: 2
Molecule	Chains	Sequence Length	Organism	Details	Image
cardiac alpha tropomyosin	F, G	135	Sus scrofa	Mutation(s): 0

Small Molecules

Ligands 2 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram
ADP	A, B, C, D, E	ADENOSINE-5'-DIPHOSPHATE C10 H15 N5 O10 P2 XTWYTFMLZFPYCI-KQYNXXCUSA-N
MG	A, B, C, D, E	MAGNESIUM ION Mg JLVVSXFLKOJNIY-UHFFFAOYSA-N

Experimental Data & Validation

Experimental Data

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

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 2017-04-12 
• Released Date: 2017-07-19 
Deposition Author(s): Risi, C., Eisner, J., Belknap, B., Heeley, D.H., White, H.D., Schroeder, G.F., Galkin, V.E.

Revision History 

• 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