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- EMDB-73993: Helical Reconstruction of the Human Cardiac F-Actin-Tropomyosin C... -

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Basic information

Entry
Database: EMDB / ID: EMD-73993
TitleHelical Reconstruction of the Human Cardiac F-Actin-Tropomyosin Complex
Map dataWT Human Actin, Tropomyosin, Cardiac
Sample
  • Complex: Complex of Cardiac F-Actin Containing Mg-ADP with Tropomyosin
    • Protein or peptide: Actin, alpha cardiac muscle 1
    • Protein or peptide: Tropomyosin alpha-1 chain
  • Ligand: ADENOSINE-5'-DIPHOSPHATE
  • Ligand: MAGNESIUM ION
KeywordsF-actin / tropomyosin / muscle / cryo-EM structure / motor proteins / MOTOR PROTEIN
Function / homology
Function and homology information


positive regulation of heart rate by epinephrine / muscle thin filament tropomyosin / actin filament-based movement / actin-myosin filament sliding / cardiac myofibril assembly / regulation of muscle contraction / bleb / Formation of the dystrophin-glycoprotein complex (DGC) / ruffle organization / cardiac muscle tissue morphogenesis ...positive regulation of heart rate by epinephrine / muscle thin filament tropomyosin / actin filament-based movement / actin-myosin filament sliding / cardiac myofibril assembly / regulation of muscle contraction / bleb / Formation of the dystrophin-glycoprotein complex (DGC) / ruffle organization / cardiac muscle tissue morphogenesis / Striated Muscle Contraction / actomyosin structure organization / muscle filament sliding / I band / sarcomere organization / structural constituent of muscle / RHOB GTPase cycle / ventricular cardiac muscle tissue morphogenesis / microfilament motor activity / heart contraction / myosin binding / negative regulation of vascular associated smooth muscle cell migration / regulation of heart contraction / mesenchyme migration / negative regulation of vascular associated smooth muscle cell proliferation / skeletal muscle thin filament assembly / RHOA GTPase cycle / Smooth Muscle Contraction / cardiac muscle contraction / stress fiber / cytoskeletal protein binding / positive regulation of stress fiber assembly / cytoskeleton organization / positive regulation of cell adhesion / actin filament organization / negative regulation of cell migration / sarcomere / cellular response to reactive oxygen species / actin filament / filopodium / wound healing / structural constituent of cytoskeleton / Hydrolases; Acting on acid anhydrides; Acting on acid anhydrides to facilitate cellular and subcellular movement / ruffle membrane / actin filament binding / regulation of cell shape / actin cytoskeleton / lamellipodium / actin binding / cell body / response to ethanol / blood microparticle / cytoskeleton / hydrolase activity / response to xenobiotic stimulus / protein heterodimerization activity / focal adhesion / positive regulation of gene expression / negative regulation of apoptotic process / glutamatergic synapse / protein homodimerization activity / extracellular space / extracellular exosome / ATP binding / identical protein binding / membrane / cytosol / cytoplasm
Similarity search - Function
Tropomyosins signature. / Tropomyosin / Tropomyosin / Actins signature 1. / Actin, conserved site / Actins signature 2. / Actin/actin-like conserved site / Actins and actin-related proteins signature. / Actin / Actin family ...Tropomyosins signature. / Tropomyosin / Tropomyosin / Actins signature 1. / Actin, conserved site / Actins signature 2. / Actin/actin-like conserved site / Actins and actin-related proteins signature. / Actin / Actin family / Actin / ATPase, nucleotide binding domain
Similarity search - Domain/homology
Tropomyosin alpha-1 chain / Actin, alpha cardiac muscle 1
Similarity search - Component
Biological speciesHomo sapiens (human)
Methodhelical reconstruction / cryo EM / Resolution: 2.79 Å
AuthorsKarpicheva O / Rynkiewicz MJ / Lehman W / Cammarato A
Funding support United States, 2 items
OrganizationGrant numberCountry
National Institutes of Health/National Heart, Lung, and Blood Institute (NIH/NHLBI)HL036153 United States
National Institutes of Health/National Heart, Lung, and Blood Institute (NIH/NHLBI)HL124091 United States
CitationJournal: J Mol Cell Cardiol / Year: 2025
Title: Pseudo-acetylation of ACTC1 K326 and K328 promotes dysinhibition of reconstituted human cardiac thin filaments.
Authors: Kripa Chitre / Olga E Karpicheva / Chloe J King / Michael J Rynkiewicz / Axel J Fenwick / John F Dawson / D Brian Foster / William Lehman / Anthony Cammarato /
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 ...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. 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.
History
DepositionNov 20, 2025-
Header (metadata) releaseJan 14, 2026-
Map releaseJan 14, 2026-
UpdateJan 14, 2026-
Current statusJan 14, 2026Processing site: RCSB / Status: Released

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Structure visualization

Supplemental images

emd_73993.png

Downloads & links

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Map

FileDownload / File: emd_73993.map.gz / Format: CCP4 / Size: 103 MB / Type: IMAGE STORED AS FLOATING POINT NUMBER (4 BYTES)
AnnotationWT Human Actin, Tropomyosin, Cardiac
Projections & slices

Image control

Size
Brightness
Contrast
Others
AxesZ (Sec.)Y (Row.)X (Col.)
0.89 Å/pix.
x 300 pix.
= 267. Å		0.89 Å/pix.
x 300 pix.
= 267. Å		0.89 Å/pix.
x 300 pix.
= 267. Å

Surface

Projections

Slices (1/3)

Slices (1/2)

Slices (2/3)

Images are generated by Spider.

Voxel sizeX=Y=Z: 0.89 Å
Density

Histogram

Histogram (log scale)
Contour LevelBy AUTHOR: 0.0796
Minimum - Maximum-0.13565306 - 0.43038404
Average (Standard dev.)0.0014374455 (±0.017669208)
SymmetrySpace group: 1
Details

EMDB XML:

Map geometry
Axis orderXYZ
Origin000
Dimensions300300300
Spacing300300300
CellA=B=C: 267.0 Å
α=β=γ: 90.0 °

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Supplemental data

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Mask #1

Fileemd_73993_msk_1.map
Projections & Slices
AxesZYX

Projections

Slices (1/2)
Density Histograms

Histogram

Histogram (log scale)

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Half map: #2

Fileemd_73993_half_map_1.map
Projections & Slices
AxesZYX

Projections

Slices (1/2)
Density Histograms

Histogram

Histogram (log scale)

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Half map: #1

Fileemd_73993_half_map_2.map
Projections & Slices
AxesZYX

Projections

Slices (1/2)
Density Histograms

Histogram

Histogram (log scale)

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Sample components

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Entire : Complex of Cardiac F-Actin Containing Mg-ADP with Tropomyosin

EntireName: Complex of Cardiac F-Actin Containing Mg-ADP with Tropomyosin
Components
  • Complex: Complex of Cardiac F-Actin Containing Mg-ADP with Tropomyosin
    • Protein or peptide: Actin, alpha cardiac muscle 1
    • Protein or peptide: Tropomyosin alpha-1 chain
  • Ligand: ADENOSINE-5'-DIPHOSPHATE
  • Ligand: MAGNESIUM ION

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Supramolecule #1: Complex of Cardiac F-Actin Containing Mg-ADP with Tropomyosin

SupramoleculeName: Complex of Cardiac F-Actin Containing Mg-ADP with Tropomyosin
type: complex / ID: 1 / Parent: 0 / Macromolecule list: #1-#2
Source (natural)Organism: Homo sapiens (human)

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Macromolecule #1: Actin, alpha cardiac muscle 1

MacromoleculeName: Actin, alpha cardiac muscle 1 / type: protein_or_peptide / ID: 1 / Number of copies: 6 / Enantiomer: LEVO
EC number: Hydrolases; Acting on acid anhydrides; Acting on acid anhydrides to facilitate cellular and subcellular movement
Source (natural)Organism: Homo sapiens (human)
Molecular weightTheoretical: 42.064891 KDa
Recombinant expressionOrganism: Spodoptera frugiperda (fall armyworm)
SequenceString: MCDDEETTAL VCDNGSGLVK AGFAGDDAPR AVFPSIVGRP RHQGVMVGMG QKDSYVGDEA QSKRGILTLK YPIEHGIITN WDDMEKIWH HTFYNELRVA PEEHPTLLTE APLNPKANRE KMTQIMFETF NVPAMYVAIQ AVLSLYASGR TTGIVLDSGD G VTHNVPIY ...String:
MCDDEETTAL VCDNGSGLVK AGFAGDDAPR AVFPSIVGRP RHQGVMVGMG QKDSYVGDEA QSKRGILTLK YPIEHGIITN WDDMEKIWH HTFYNELRVA PEEHPTLLTE APLNPKANRE KMTQIMFETF NVPAMYVAIQ AVLSLYASGR TTGIVLDSGD G VTHNVPIY EGYALPHAIM RLDLAGRDLT DYLMKILTER GYSFVTTAER EIVRDIKEKL CYVALDFENE MATAASSSSL EK SYELPDG QVITIGNERF RCPETLFQPS FIGMESAGIH ETTYNSIMKC DIDIRKDLYA NNVLSGGTTM YPGIADRMQK EIT ALAPST MKIKIIAPPE RKYSVWIGGS ILASLSTFQQ MWISKQEYDE AGPSIVHRKC F

UniProtKB: Actin, alpha cardiac muscle 1

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Macromolecule #2: Tropomyosin alpha-1 chain

MacromoleculeName: Tropomyosin alpha-1 chain / type: protein_or_peptide / ID: 2 / Number of copies: 4 / Enantiomer: LEVO
Source (natural)Organism: Homo sapiens (human)
Molecular weightTheoretical: 32.921773 KDa
Recombinant expressionOrganism: Escherichia coli BL21(DE3) (bacteria)
SequenceString: ASMDAIKKKM QMLKLDKENA LDRAEQAEAD KKAAEDRSKQ LEDELVSLQK KLKGTEDELD KYSEALKDAQ EKLELAEKKA TDAEADVAS LNRRIQLVEE ELDRAQERLA TALQKLEEAE KAADESERGM KVIESRAQKD EEKMEIQEIQ LKEAKHIAED A DRKYEEVA ...String:
ASMDAIKKKM QMLKLDKENA LDRAEQAEAD KKAAEDRSKQ LEDELVSLQK KLKGTEDELD KYSEALKDAQ EKLELAEKKA TDAEADVAS LNRRIQLVEE ELDRAQERLA TALQKLEEAE KAADESERGM KVIESRAQKD EEKMEIQEIQ LKEAKHIAED A DRKYEEVA RKLVIIESDL ERAEERAELS EGKCAELEEE LKTVTNNLKS LEAQAEKYSQ KEDRYEEEIK VLSDKLKEAE TR AEFAERS VTKLEKSIDD LEDELYAQKL KYKAISEELD HALNDMTSI

UniProtKB: Tropomyosin alpha-1 chain

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Macromolecule #3: ADENOSINE-5'-DIPHOSPHATE

MacromoleculeName: ADENOSINE-5'-DIPHOSPHATE / type: ligand / ID: 3 / Number of copies: 6 / Formula: ADP
Molecular weightTheoretical: 427.201 Da
Chemical component information

ChemComp-ADP:
ADENOSINE-5'-DIPHOSPHATE / ADP, energy-carrying molecule*YM

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Macromolecule #4: MAGNESIUM ION

MacromoleculeName: MAGNESIUM ION / type: ligand / ID: 4 / Number of copies: 6 / Formula: MG
Molecular weightTheoretical: 24.305 Da

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Experimental details

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Structure determination

Methodcryo EM
Processinghelical reconstruction
Aggregation statefilament

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Sample preparation

BufferpH: 7
Component:
ConcentrationFormulaName
10.0 mMC7H15NO4S3-(N-morpholino)propanesulfonic acid
50.0 mMCH3COONaSodium acetate
3.0 mMMgCl2Magnesium chloride
1.0 mMC4H10O2S2Dithiothreitol
GridModel: Quantifoil R1.2/1.3 / Material: COPPER / Mesh: 300 / Support film - Material: CARBON / Support film - topology: HOLEY / Support film - Film thickness: 11 / Pretreatment - Type: GLOW DISCHARGE / Pretreatment - Time: 45 sec. / Pretreatment - Pressure: 0.02 kPa
VitrificationCryogen name: ETHANE / Chamber humidity: 100 % / Chamber temperature: 283 K / Instrument: FEI VITROBOT MARK IV
Details: Blotting was performed with a blot force of 3 and a blot time of 3 s..
Details9 uM F-actin was mixed with 63 uM tropomyosin and incubated for 15 minutes; then 3 uL of the mixture was applied to the grid

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Electron microscopy

MicroscopeTFS GLACIOS
TemperatureMin: 98.0 K / Max: 98.0 K
Specialist opticsPhase plate: OTHER / Energy filter - Name: TFS Selectris
SoftwareName: cryoSPARC (ver. v4.5.3)
Image recordingFilm or detector model: FEI FALCON IV (4k x 4k) / Number grids imaged: 1 / Number real images: 4731 / Average electron dose: 48.96 e/Å2
Electron beamAcceleration voltage: 200 kV / Electron source: FIELD EMISSION GUN
Electron opticsC2 aperture diameter: 50.0 µm / Illumination mode: FLOOD BEAM / Imaging mode: BRIGHT FIELD / Cs: 2.7 mm / Nominal defocus max: 2.5 µm / Nominal defocus min: 0.8 µm / Nominal magnification: 130000
Sample stageSpecimen holder model: OTHER / Cooling holder cryogen: NITROGEN

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Image processing

Final reconstructionNumber classes used: 21
Applied symmetry - Helical parameters - Δz: 27.67 Å
Applied symmetry - Helical parameters - Δ&Phi: -166.52 °
Applied symmetry - Helical parameters - Axial symmetry: C3 (3 fold cyclic)
Resolution.type: BY AUTHOR / Resolution: 2.79 Å / Resolution method: FSC 0.143 CUT-OFF / Software - Name: cryoSPARC (ver. v4.5.3) / Number images used: 1954406
CTF correctionSoftware - Name: cryoSPARC (ver. v4.5.3) / Type: PHASE FLIPPING AND AMPLITUDE CORRECTION
Segment selectionNumber selected: 2655073 / Software - Name: cryoSPARC (ver. v4.5.3)
Software - details: Filaments were collected using Filament Tracer Tool
Startup modelType of model: NONE
FSC plot (resolution estimation)

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Atomic model buiding 1

Initial modelPDB ID:

5jlf


Chain - Source name: PDB / Chain - Initial model type: experimental model
SoftwareName: MDFF (ver. 1.9.4a53)
RefinementProtocol: FLEXIBLE FIT
Output model

PDB-9zbl:
Helical Reconstruction of the Human Cardiac F-Actin-Tropomyosin Complex

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