Biological Assembly 1  

 3D View: Structure | Ligand Interaction

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Hetero 29-mer - A15B4C4D2E2F2 Pseudo Symmetry: Asymmetric - C1 
Pseudo Stoichiometry: Hetero 29-mer - A15B4C2D2E2F2G2 

Biological assembly 1 assigned by authors.

Macromolecule Content

• Total Structure Weight: 883.01 kDa 
• Atom Count: 60966 
• Modelled Residue Count: 7669 
• Deposited Residue Count: 7765 
• Unique protein chains: 6

6KN8

Structure of human cardiac thin filament in the calcium bound state

• DOI: 10.2210/pdb6KN8/pdb
• EMDataResource: EMD-0729

• Classification: CONTRACTILE PROTEIN/ACTIN BINDING PROTEIN
• Organism(s): Oryctolagus cuniculus, Homo sapiens
• Expression System: Escherichia coli
• Mutation(s): No 


• Deposited: 2019-08-03 Released: 2020-01-15 
• Deposition Author(s): Fujii, T., Yamada, Y., Namba, K.

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Experimental Data Snapshot

• Method: ELECTRON MICROSCOPY
• Resolution: 4.80 Å
• Aggregation State: FILAMENT 
• Reconstruction Method: SINGLE PARTICLE 

Literature

Cardiac muscle thin filament structures reveal calcium regulatory mechanism.

Yamada, Y., Namba, K., Fujii, T.

(2020) Nat Commun 11: 153-153

• PubMed: 31919429 
• DOI: 10.1038/s41467-019-14008-1
• Primary Citation of Related Structures:  
  6KN8, 6KN7


• PubMed Abstract: 
  

Contraction of striated muscles is driven by cyclic interactions of myosin head projecting from the thick filament with actin filament and is regulated by Ca ²⁺ released from sarcoplasmic reticulum. Muscle thin filament consists of actin, tropomyosin and troponin, and Ca ²⁺ binding to troponin triggers conformational changes of troponin and tropomyosin to allow actin-myosin interactions. However, the structural changes involved in this regulatory mechanism remain unknown. Here we report the structures of human cardiac muscle thin filament in the absence and presence of Ca ²⁺ by electron cryomicroscopy. Molecular models in the two states built based on available crystal structures reveal the structures of a C-terminal region of troponin I and an N-terminal region of troponin T in complex with the head-to-tail junction of tropomyosin together with the troponin core on actin filament. Structural changes of the thin filament upon Ca ²⁺ binding now reveal the mechanism of Ca ²⁺ regulation of muscle contraction.

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Organizational Affiliation: 

JEOL YOKOGUSHI Research Alliance Laboratories, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan. [e-mail].

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
Actin, alpha skeletal muscle	A,  B,  C,  D,  E,  F,  G,  H,  I,  J,  K,  L,  M,  N,  O	375	Oryctolagus cuniculus	Mutation(s): 0  Gene Names: ACTA1, ACTA
Find proteins for P68135 (Oryctolagus cuniculus) Explore P68135  Go to UniProtKB:  P68135

Entity ID: 2
Molecule	Chains	Sequence Length	Organism	Details	Image
Tropomyosin alpha-1 chain	P, Q, W, X	274	Homo sapiens	Mutation(s): 0  Gene Names: TPM1, C15orf13, TMSA
Find proteins for P09493 (Homo sapiens) Explore P09493  Go to UniProtKB:  P09493
NIH Common Fund Data Resources
PHAROS:  P09493 GTEx:  ENSG00000140416

Entity ID: 3
Molecule	Chains	Sequence Length	Organism	Details	Image
Tropomyosin alpha-1 chain	R, S, Y, Z	31	Homo sapiens	Mutation(s): 0  Gene Names: TPM1, C15orf13, TMSA
Find proteins for P09493 (Homo sapiens) Explore P09493  Go to UniProtKB:  P09493
NIH Common Fund Data Resources
PHAROS:  P09493 GTEx:  ENSG00000140416

Entity ID: 4
Molecule	Chains	Sequence Length	Organism	Details	Image
Troponin T, cardiac muscle	T, a	174	Homo sapiens	Mutation(s): 0  Gene Names: TNNT2
Find proteins for P45379 (Homo sapiens) Explore P45379  Go to UniProtKB:  P45379
NIH Common Fund Data Resources
PHAROS:  P45379 GTEx:  ENSG00000118194

Entity ID: 5
Molecule	Chains	Sequence Length	Organism	Details	Image
Troponin I, cardiac muscle	U, b	126	Homo sapiens	Mutation(s): 0  Gene Names: TNNI3, TNNC1
Find proteins for P19429 (Homo sapiens) Explore P19429  Go to UniProtKB:  P19429
NIH Common Fund Data Resources
PHAROS:  P19429 GTEx:  ENSG00000129991

Entity ID: 6
Molecule	Chains	Sequence Length	Organism	Details	Image
Troponin C, slow skeletal and cardiac muscles	V, c	160	Homo sapiens	Mutation(s): 0  Gene Names: TNNC1, TNNC
Find proteins for P63316 (Homo sapiens) Explore P63316  Go to UniProtKB:  P63316
NIH Common Fund Data Resources
PHAROS:  P63316 GTEx:  ENSG00000114854

Small Molecules

Ligands 1 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram
ADP	A, B, C, D, E, F, G, H, I, J, K, L, M, N, O	ADENOSINE-5'-DIPHOSPHATE C10 H15 N5 O10 P2 XTWYTFMLZFPYCI-KQYNXXCUSA-N

Experimental Data & Validation

Experimental Data

• Method: ELECTRON MICROSCOPY
• Resolution: 4.80 Å
• Aggregation State: FILAMENT 
• Reconstruction Method: SINGLE PARTICLE 

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 2019-08-03 
• Released Date: 2020-01-15 
Deposition Author(s): Fujii, T., Yamada, Y., Namba, K.

Revision History  

• Version 1.0: 2020-01-15
  Type: Initial release
  
• Version 1.1: 2020-01-22
  Changes: Database references