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Open data
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Basic information
Entry | Database: PDB / ID: 5ljv | |||||||||
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Title | MamK double helical filament | |||||||||
![]() | Actin-like ATPase | |||||||||
![]() | STRUCTURAL PROTEIN / bacterial cytoskeleton / filamentous protein / actin-like / magnetosomes | |||||||||
Function / homology | ![]() magnetosome assembly / magnetosome membrane / Hydrolases; Acting on acid anhydrides; In phosphorus-containing anhydrides / cytoskeleton / GTP binding / ATP hydrolysis activity / ATP binding / metal ion binding / cytoplasm Similarity search - Function | |||||||||
Biological species | ![]() | |||||||||
Method | ELECTRON MICROSCOPY / helical reconstruction / cryo EM / Resolution: 3.64 Å | |||||||||
![]() | Lowe, J. | |||||||||
Funding support | ![]()
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![]() | ![]() Title: X-ray and cryo-EM structures of monomeric and filamentous actin-like protein MamK reveal changes associated with polymerization. Authors: Jan Löwe / Shaoda He / Sjors H W Scheres / Christos G Savva / ![]() Abstract: Magnetotactic bacteria produce iron-rich magnetic nanoparticles that are enclosed by membrane invaginations to form magnetosomes so they are able to sense and act upon Earth's magnetic field. In ...Magnetotactic bacteria produce iron-rich magnetic nanoparticles that are enclosed by membrane invaginations to form magnetosomes so they are able to sense and act upon Earth's magnetic field. In Magnetospirillum and other magnetotactic bacteria, to combine their magnetic moments, magnetosomes align along filaments formed by a bacterial actin homolog, MamK. Here, we present the crystal structure of a nonpolymerizing mutant of MamK from Magnetospirillum magneticum AMB-1 at 1.8-Å resolution, revealing its close similarity to actin and MreB. The crystals contain AMPPNP-bound monomeric MamK in two different conformations. To investigate conformational changes associated with polymerization, we used unmodified MamK protein and cryo-EM with helical 3D reconstruction in RELION to obtain a density map and a fully refined atomic model of MamK in filamentous form at 3.6-Å resolution. The filament is parallel (polar) double-helical, with a rise of 52.2 Å and a twist of 23.8°. As shown previously and unusually for actin-like filaments, the MamK subunits from each of the two strands are juxtaposed, creating an additional twofold axis along the filament. Compared with monomeric MamK, ADP-bound MamK in the filament undergoes a conformational change, rotating domains I and II against each other to further close the interdomain cleft between subdomains IB and IIB. The domain movement causes several loops to close around the nucleotide-binding pocket. Glu-143, a key residue for catalysis coordinating the magnesium ion, moves closer, presumably switching nucleotide hydrolysis upon polymerization-one of the hallmarks of cytomotive filaments of the actin type. | |||||||||
History |
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Structure visualization
Movie |
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Structure viewer | Molecule: ![]() ![]() |
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Downloads & links
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Download
PDBx/mmCIF format | ![]() | 382.7 KB | Display | ![]() |
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PDB format | ![]() | 310.4 KB | Display | ![]() |
PDBx/mmJSON format | ![]() | Tree view | ![]() | |
Others | ![]() |
-Validation report
Summary document | ![]() | 1.3 MB | Display | ![]() |
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Full document | ![]() | 1.4 MB | Display | |
Data in XML | ![]() | 73.8 KB | Display | |
Data in CIF | ![]() | 104 KB | Display | |
Arichive directory | ![]() ![]() | HTTPS FTP |
-Related structure data
Related structure data | ![]() 4062MC ![]() 5ljwC M: map data used to model this data C: citing same article ( |
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Similar structure data |
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Assembly
Deposited unit | ![]()
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Noncrystallographic symmetry (NCS) | NCS domain:
NCS domain segments: Component-ID: _ / Beg auth comp-ID: ASN / Beg label comp-ID: ASN / End auth comp-ID: PRO / End label comp-ID: PRO / Refine code: _ / Auth seq-ID: 10 - 334 / Label seq-ID: 10 - 334
NCS ensembles :
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Components
#1: Protein | Mass: 37642.152 Da / Num. of mol.: 6 Source method: isolated from a genetically manipulated source Source: (gene. exp.) ![]() Gene: amb0965 / Production host: ![]() ![]() #2: Chemical | ChemComp-MG / #3: Chemical | ChemComp-ADP / |
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-Experimental details
-Experiment
Experiment | Method: ELECTRON MICROSCOPY |
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EM experiment | Aggregation state: FILAMENT / 3D reconstruction method: helical reconstruction |
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Sample preparation
Component | Name: MamK / Type: COMPLEX / Entity ID: #1 / Source: RECOMBINANT |
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Source (natural) | Organism: ![]() |
Source (recombinant) | Organism: ![]() ![]() |
Buffer solution | pH: 7.4 |
Specimen | Conc.: 1.5 mg/ml / Embedding applied: NO / Shadowing applied: NO / Staining applied: NO / Vitrification applied: YES |
Specimen support | Grid material: COPPER/RHODIUM / Grid mesh size: 200 divisions/in. / Grid type: Quantifoil |
Vitrification | Instrument: FEI VITROBOT MARK IV / Cryogen name: ETHANE / Humidity: 100 % / Chamber temperature: 283 K |
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Electron microscopy imaging
Experimental equipment | ![]() Model: Tecnai Polara / Image courtesy: FEI Company |
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Microscopy | Model: FEI POLARA 300 |
Electron gun | Electron source: ![]() |
Electron lens | Mode: BRIGHT FIELD / Calibrated defocus min: 1100 nm / Calibrated defocus max: 3000 nm / C2 aperture diameter: 50 µm / Alignment procedure: COMA FREE |
Image recording | Average exposure time: 1.5 sec. / Electron dose: 40 e/Å2 / Detector mode: INTEGRATING / Film or detector model: FEI FALCON II (4k x 4k) / Num. of grids imaged: 3 / Num. of real images: 1665 |
Image scans | Width: 4000 / Height: 4000 / Movie frames/image: 46 |
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Processing
Software | Name: REFMAC / Version: 5.8.0137 / Classification: refinement | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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EM software |
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CTF correction | Type: PHASE FLIPPING AND AMPLITUDE CORRECTION | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Helical symmerty | Angular rotation/subunit: 23.77 ° / Axial rise/subunit: 52.15 Å / Axial symmetry: C2 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
3D reconstruction | Resolution: 3.64 Å / Resolution method: FSC 0.143 CUT-OFF / Num. of particles: 596427 / Symmetry type: HELICAL | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Atomic model building | Protocol: OTHER / Space: RECIPROCAL / Target criteria: R-factor | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Refinement | Resolution: 3.64→3.64 Å / Cor.coef. Fo:Fc: 0.844 / SU B: 16.854 / SU ML: 0.242 / ESU R: 0.976 Stereochemistry target values: MAXIMUM LIKELIHOOD WITH PHASES Details: HYDROGENS HAVE BEEN ADDED IN THE RIDING POSITIONS
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Solvent computation | Solvent model: PARAMETERS FOR MASK CACLULATION | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Displacement parameters | Biso mean: 108.731 Å2
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Refinement step | Cycle: 1 / Total: 15000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Refine LS restraints |
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