9ZBL | pdb_00009zbl

Helical Reconstruction of the Human Cardiac F-Actin-Tropomyosin Complex

PDB DOI: https://doi.org/10.2210/pdb9ZBL/pdb
EM Map EMD-73993: EMDB EMDataResource

Classification: MOTOR PROTEIN
Organism(s): Homo sapiens
Expression System: Spodoptera frugiperda, Escherichia coli BL21(DE3)
Mutation(s): No

Deposited: 2025-11-20 Released: 2026-01-14
Deposition Author(s): Karpicheva, O., Rynkiewicz, M.J., Lehman, W., Cammarato, A.
Funding Organization(s): National Institutes of Health/National Heart, Lung, and Blood Institute (NIH/NHLBI)

Experimental Data Snapshot

Method: ELECTRON MICROSCOPY
Resolution: 2.79 Å
Aggregation State: FILAMENT
Reconstruction Method: HELICAL

Starting Model: experimental
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wwPDB Validation 3D Report Full Report

This is version 1.0 of the entry. See complete history.

Literature

Pseudo-acetylation of ACTC1 K326 and K328 promotes dysinhibition of reconstituted human cardiac thin filaments.

Chitre, K., Karpicheva, O.E., King, C.J., Rynkiewicz, M.J., Fenwick, A.J., Dawson, J.F., Foster, D.B., Lehman, W., Cammarato, A.

(2025) J Mol Cell Cardiol 212: 10-15

PubMed: 41443503 Search on PubMed Search on PubMed Central
DOI: https://doi.org/10.1016/j.yjmcc.2025.12.008
Primary Citation Related Structures:
9ZBL, 9ZBP

PubMed Abstract:
Electrostatic interactions between actin residues K326 and K328 and tropomyosin bias tropomyosin to an F-actin location where it blocks myosin attachment. K326/328 acetylation neutralizes their charge, potentially disrupting thin filament-based contractile regulation. We verified acetylation of K326/328 on human cardiac actin (ACTC1) and generated recombinant K326/328Q, pseudo-acetylated ACTC1. Pseudo-acetylation reduced inhibition of myosin-driven motility of F-actin-tropomyosin and F-actin-tropomyosin-troponin at low Ca ²⁺. Cryo-EM-based and computational modeling revealed that pseudo-acetylation did not alter tropomyosin positioning along F-actin but decreased local F-actin-tropomyosin interaction energy. Thus, by reducing the energetic demands required for myosin to displace tropomyosin, ACTC1 K326/328 acetylation may promote contractile activation.

Organizational Affiliation

Department of Medicine, Division of Cardiology, Johns Hopkins University, 720 Rutland Avenue, Baltimore, MD 21205, USA.

Macromolecule Content

Total Structure Weight: 386.79 kDa
Atom Count: 21,570
Modeled Residue Count: 2,722
Deposited Residue Count: 3,406
Unique protein chains: 2

Macromolecules

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| 3D Structure

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
Actin, alpha cardiac muscle 1	A, B, C, D, E A, B, C, D, E, F	377	Homo sapiens	Mutation(s): 0 Gene Names: ACTC1, ACTC EC: 3.6.4
UniProt & NIH Common Fund Data Resources
Find proteins for P68032 (Homo sapiens) Explore P68032 Go to UniProtKB: P68032
PHAROS: P68032 GTEx: ENSG00000159251
Entity Groups
Sequence Clusters	30% Identity 50% Identity 70% Identity 90% Identity 95% Identity 100% Identity
UniProt Group	P68032
Sequence Annotations Expand
Reference Sequence

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| 3D Structure

Entity ID: 2
Molecule	Chains	Sequence Length	Organism	Details	Image
Tropomyosin alpha-1 chain	G [auth M], H [auth N], I [auth O], J [auth P]	286	Homo sapiens	Mutation(s): 0 Gene Names: TPM1, C15orf13, TMSA
UniProt & NIH Common Fund Data Resources
Find proteins for P09493 (Homo sapiens) Explore P09493 Go to UniProtKB: P09493
PHAROS: P09493 GTEx: ENSG00000140416
Entity Groups
Sequence Clusters	30% Identity 50% Identity 70% Identity 90% Identity 95% Identity 100% Identity
UniProt Group	P09493
Sequence Annotations Expand
Reference Sequence

Small Molecules

Ligands 2 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram	3D Interactions
ADP Query on ADP Download:Ideal Coordinates CCD File SDF format, chain U [auth F] SDF format, chain S [auth E] SDF format, chain Q [auth D] SDF format, chain O [auth C] SDF format, chain M [auth B] SDF format, chain K [auth A] MOL2 format, chain U [auth F] MOL2 format, chain S [auth E] MOL2 format, chain Q [auth D] MOL2 format, chain O [auth C] MOL2 format, chain M [auth B] MOL2 format, chain K [auth A] mmCIF format, chain U [auth F] mmCIF format, chain S [auth E] mmCIF format, chain Q [auth D] mmCIF format, chain O [auth C] mmCIF format, chain M [auth B] mmCIF format, chain K [auth A]	K [auth A] M [auth B] O [auth C] Q [auth D] S [auth E] K [auth A], M [auth B], O [auth C], Q [auth D], S [auth E], U [auth F]	ADENOSINE-5'-DIPHOSPHATE C₁₀ H₁₅ N₅ O₁₀ P₂ XTWYTFMLZFPYCI-KQYNXXCUSA-N		Interactions Focus chain K [auth A] Focus chain M [auth B] Focus chain O [auth C] Focus chain Q [auth D] Focus chain S [auth E] Focus chain U [auth F] Interactions & Density Focus chain K [auth A] Focus chain M [auth B] Focus chain O [auth C] Focus chain Q [auth D] Focus chain S [auth E] Focus chain U [auth F]
MG Query on MG Download:Ideal Coordinates CCD File SDF format, chain V [auth F] SDF format, chain T [auth E] SDF format, chain R [auth D] SDF format, chain P [auth C] SDF format, chain N [auth B] SDF format, chain L [auth A] MOL2 format, chain V [auth F] MOL2 format, chain T [auth E] MOL2 format, chain R [auth D] MOL2 format, chain P [auth C] MOL2 format, chain N [auth B] MOL2 format, chain L [auth A] mmCIF format, chain V [auth F] mmCIF format, chain T [auth E] mmCIF format, chain R [auth D] mmCIF format, chain P [auth C] mmCIF format, chain N [auth B] mmCIF format, chain L [auth A]	L [auth A] N [auth B] P [auth C] R [auth D] T [auth E] L [auth A], N [auth B], P [auth C], R [auth D], T [auth E], V [auth F]	MAGNESIUM ION Mg JLVVSXFLKOJNIY-UHFFFAOYSA-N		Interactions Focus chain L [auth A] Focus chain N [auth B] Focus chain P [auth C] Focus chain R [auth D] Focus chain T [auth E] Focus chain V [auth F] Interactions & Density Focus chain L [auth A] Focus chain N [auth B] Focus chain P [auth C] Focus chain R [auth D] Focus chain T [auth E] Focus chain V [auth F]

Experimental Data & Validation

Experimental Data

Method: ELECTRON MICROSCOPY
Resolution: 2.79 Å
Aggregation State: FILAMENT
Reconstruction Method: HELICAL

EM Software:

Task	Software Package	Version
RECONSTRUCTION	cryoSPARC	v4.5.3
MODEL REFINEMENT	PHENIX	2.0.5867

Structure Validation

View Full Validation Report

View more in-depth experimental data

Entry History

& Funding Information

Deposition Data

Released Date: 2026-01-14

Deposition Author(s):

Funding Organization	Location	Grant Number
National Institutes of Health/National Heart, Lung, and Blood Institute (NIH/NHLBI)	United States	HL036153
National Institutes of Health/National Heart, Lung, and Blood Institute (NIH/NHLBI)	United States	HL124091