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- PDB-9ax8: 70S initiation complex (tRNA-fMet M1, initiation factor 2 + CUG s... -
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Open data
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Basic information
Entry | Database: PDB / ID: 9ax8 | ||||||||||||||||||
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Title | 70S initiation complex (tRNA-fMet M1, initiation factor 2 + CUG start codon) | ||||||||||||||||||
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![]() | RIBOSOME / translation initiation / tRNA-fMet M1 / frameshifting / initiation factor 2 | ||||||||||||||||||
Function / homology | ![]() guanosine tetraphosphate binding / DnaA-L2 complex / negative regulation of DNA-templated DNA replication initiation / translation initiation factor activity / assembly of large subunit precursor of preribosome / ribosome assembly / cytosolic ribosome assembly / mRNA 5'-UTR binding / large ribosomal subunit / transferase activity ...guanosine tetraphosphate binding / DnaA-L2 complex / negative regulation of DNA-templated DNA replication initiation / translation initiation factor activity / assembly of large subunit precursor of preribosome / ribosome assembly / cytosolic ribosome assembly / mRNA 5'-UTR binding / large ribosomal subunit / transferase activity / ribosomal small subunit biogenesis / ribosomal small subunit assembly / small ribosomal subunit / 5S rRNA binding / ribosomal large subunit assembly / cytosolic small ribosomal subunit / large ribosomal subunit rRNA binding / small ribosomal subunit rRNA binding / cytosolic large ribosomal subunit / cytoplasmic translation / tRNA binding / negative regulation of translation / rRNA binding / ribosome / structural constituent of ribosome / translation / ribonucleoprotein complex / response to antibiotic / GTPase activity / mRNA binding / GTP binding / RNA binding / zinc ion binding / membrane / cytosol / cytoplasm Similarity search - Function | ||||||||||||||||||
Biological species | ![]() ![]() | ||||||||||||||||||
Method | ELECTRON MICROSCOPY / single particle reconstruction / cryo EM / Resolution: 2.6 Å | ||||||||||||||||||
![]() | Mattingly, J.M. / Nguyen, H.A. / Dunham, C.M. | ||||||||||||||||||
Funding support | ![]()
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![]() | ![]() Title: Structural analysis of noncanonical translation initiation complexes. Authors: Jacob M Mattingly / Ha An Nguyen / Bappaditya Roy / Kurt Fredrick / Christine M Dunham / ![]() Abstract: Translation initiation is a highly regulated, multi-step process that is critical for efficient and accurate protein synthesis. In bacteria, initiation begins when mRNA, initiation factors, and a ...Translation initiation is a highly regulated, multi-step process that is critical for efficient and accurate protein synthesis. In bacteria, initiation begins when mRNA, initiation factors, and a dedicated initiator fMet-tRNA bind the small (30S) ribosomal subunit. Specific binding of fMet-tRNA in the peptidyl (P) site is mediated by the inspection of the fMet moiety by initiation factor IF2 and of three conserved G-C base pairs in the tRNA anticodon stem by the 30S head domain. Tandem A-minor interactions form between 16S ribosomal RNA nucleotides A1339 and G1338 and tRNA base pairs G30-C40 and G29-C41, respectively. Swapping the G30-C40 pair of tRNA with C-G (called tRNA M1) reduces discrimination against the noncanonical start codon CUG in vitro, suggesting crosstalk between the gripping of the anticodon stem and recognition of the start codon. Here, we solved electron cryomicroscopy structures of Escherichia coli 70S initiation complexes containing the fMet-tRNA M1 variant paired to the noncanonical CUG start codon, in the presence or absence of IF2 and the non-hydrolyzable GTP analog GDPCP, alongside structures of 70S initiation complexes containing this tRNA variant paired to the canonical bacterial start codons AUG, GUG, and UUG. We find that the M1 mutation weakens A-minor interactions between tRNA and 16S nucleotides A1339 and G1338, with IF2 strengthening the interaction of G1338 with the tRNA minor groove. These structures suggest how even slight changes to the recognition of the fMet-tRNA anticodon stem by the ribosome can impact the start codon selection. | ||||||||||||||||||
History |
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Structure visualization
Structure viewer | Molecule: ![]() ![]() |
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Downloads & links
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Download
PDBx/mmCIF format | ![]() | 3.6 MB | Display | ![]() |
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PDB format | ![]() | Display | ![]() | |
PDBx/mmJSON format | ![]() | Tree view | ![]() | |
Others | ![]() |
-Validation report
Arichive directory | ![]() ![]() | HTTPS FTP |
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-Related structure data
Related structure data | ![]() 43930MC ![]() 9ax7C ![]() 9cg5C ![]() 9cg6C ![]() 9cg7C C: citing same article ( M: map data used to model this data |
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Similar structure data | Similarity search - Function & homology ![]() |
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Links
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Assembly
Deposited unit | ![]()
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1 |
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Components
+50S ribosomal protein ... , 27 types, 27 molecules 0123456789EFHJKLMNOPQRSTUVY
-RNA chain , 5 types, 5 molecules XaxyA
#27: RNA chain | Mass: 38177.762 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
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#29: RNA chain | Mass: 498725.406 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#50: RNA chain | Mass: 8706.247 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#51: RNA chain | Mass: 24786.785 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#53: RNA chain | Mass: 935101.562 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
-30S ribosomal protein ... , 20 types, 20 molecules bcdefghijklmnopqrstu
#30: Protein | Mass: 24253.943 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
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#31: Protein | Mass: 23078.785 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#32: Protein | Mass: 23383.002 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#33: Protein | Mass: 15804.282 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#34: Protein | Mass: 11669.371 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#35: Protein | Mass: 16861.523 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#36: Protein | Mass: 14015.361 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#37: Protein | Mass: 14554.882 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#38: Protein | Mass: 11196.988 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#39: Protein | Mass: 12487.200 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#40: Protein | Mass: 13636.961 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#41: Protein | Mass: 12625.753 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#42: Protein | Mass: 7117.352 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#43: Protein | Mass: 10159.621 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#44: Protein | Mass: 9207.572 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#45: Protein | Mass: 9263.946 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#46: Protein | Mass: 6328.330 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#47: Protein | Mass: 9057.626 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#48: Protein | Mass: 9506.190 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
#49: Protein | Mass: 6067.081 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
-Protein , 1 types, 1 molecules z
#52: Protein | Mass: 54866.508 Da / Num. of mol.: 1 / Source method: isolated from a natural source / Source: (natural) ![]() ![]() |
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-Non-polymers , 2 types, 288 molecules 


#54: Chemical | ChemComp-MG / #55: Chemical | ChemComp-GCP / | |
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-Details
Has ligand of interest | N |
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Has protein modification | N |
-Experimental details
-Experiment
Experiment | Method: ELECTRON MICROSCOPY |
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EM experiment | Aggregation state: PARTICLE / 3D reconstruction method: single particle reconstruction |
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Sample preparation
Component | Name: E. coli 70S ribosome in complex with fMet-tRNA-fMet M1, initiation factor 2, and mRNA containing P-site CUG start codon and A-site GUA codon Type: RIBOSOME / Entity ID: #1-#53 / Source: NATURAL |
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Molecular weight | Experimental value: NO |
Source (natural) | Organism: ![]() ![]() |
Buffer solution | pH: 7.5 |
Specimen | Embedding applied: NO / Shadowing applied: NO / Staining applied: NO / Vitrification applied: YES |
Specimen support | Grid material: GOLD / Grid mesh size: 300 divisions/in. / Grid type: C-flat-1.2/1.3 |
Vitrification | Cryogen name: ETHANE |
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Electron microscopy imaging
Experimental equipment | ![]() Model: Titan Krios / Image courtesy: FEI Company |
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Microscopy | Model: TFS KRIOS |
Electron gun | Electron source: ![]() |
Electron lens | Mode: BRIGHT FIELD / Nominal defocus max: 2500 nm / Nominal defocus min: 500 nm |
Image recording | Electron dose: 50 e/Å2 / Film or detector model: TFS FALCON 4i (4k x 4k) |
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Processing
EM software |
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CTF correction | Type: PHASE FLIPPING AND AMPLITUDE CORRECTION | |||||||||||||||||||||||||
3D reconstruction | Resolution: 2.6 Å / Resolution method: FSC 0.143 CUT-OFF / Num. of particles: 42825 / Symmetry type: POINT | |||||||||||||||||||||||||
Atomic model building | PDB-ID: 6O9K Accession code: 6O9K / Source name: PDB / Type: experimental model |