Journal: Nucleic Acids Res / Year: 2018 Title: Structure of a human cap-dependent 48S translation pre-initiation complex. Authors: Boris Eliseev / Lahari Yeramala / Alexander Leitner / Manikandan Karuppasamy / Etienne Raimondeau / Karine Huard / Elena Alkalaeva / Ruedi Aebersold / Christiane Schaffitzel / Abstract: Eukaryotic translation initiation is tightly regulated, requiring a set of conserved initiation factors (eIFs). Translation of a capped mRNA depends on the trimeric eIF4F complex and eIF4B to load ...Eukaryotic translation initiation is tightly regulated, requiring a set of conserved initiation factors (eIFs). Translation of a capped mRNA depends on the trimeric eIF4F complex and eIF4B to load the mRNA onto the 43S pre-initiation complex comprising 40S and initiation factors 1, 1A, 2, 3 and 5 as well as initiator-tRNA. Binding of the mRNA is followed by mRNA scanning in the 48S pre-initiation complex, until a start codon is recognised. Here, we use a reconstituted system to prepare human 48S complexes assembled on capped mRNA in the presence of eIF4B and eIF4F. The highly purified h-48S complexes are used for cross-linking/mass spectrometry, revealing the protein interaction network in this complex. We report the electron cryo-microscopy structure of the h-48S complex at 6.3 Å resolution. While the majority of eIF4B and eIF4F appear to be flexible with respect to the ribosome, additional density is detected at the entrance of the 40S mRNA channel which we attribute to the RNA-recognition motif of eIF4B. The eight core subunits of eIF3 are bound at the 40S solvent-exposed side, as well as the subunits eIF3d, eIF3b and eIF3i. elF2 and initiator-tRNA bound to the start codon are present at the 40S intersubunit side. This cryo-EM structure represents a molecular snap-shot revealing the h-48S complex following start codon recognition.
History
Deposition
Jan 16, 2018
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Header (metadata) release
Mar 7, 2018
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Map release
Mar 7, 2018
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Update
Mar 14, 2018
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Current status
Mar 14, 2018
Processing site: PDBe / Status: Released
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Structure visualization
Movie
Surface view with section colored by density value
Entire : human cap-dependent 48S translation pre-initiation complex
Entire
Name: human cap-dependent 48S translation pre-initiation complex
Components
Complex: human cap-dependent 48S translation pre-initiation complex
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Supramolecule #1: human cap-dependent 48S translation pre-initiation complex
Supramolecule
Name: human cap-dependent 48S translation pre-initiation complex type: complex / ID: 1 / Parent: 0 / Macromolecule list: #1-#50 Details: This map comprises human 40S, mRNA, initiator tRNA, eIF2 and eIF4B RRM obtained from multiple sources as described in the publication.
Source (natural)
Organism: Homo sapiens (human)
Molecular weight
Theoretical: 2.0 MDa
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Experimental details
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Structure determination
Method
cryo EM
Processing
single particle reconstruction
Aggregation state
particle
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Sample preparation
Buffer
pH: 7.5 Details: 20 mM Tris HCl, 50 mM KOAc, 2.5 mM MgCl2, 2 mM DTT, 0.25 mM spermidine 0.25 mM GMPPNP
Grid
Model: Quantifoil R2/2
Vitrification
Cryogen name: ETHANE / Chamber humidity: 100 % / Chamber temperature: 277 K / Instrument: FEI VITROBOT MARK IV
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Electron microscopy
Microscope
FEI TITAN KRIOS
Image recording
Film or detector model: FEI FALCON II (4k x 4k) / Detector mode: INTEGRATING / Average electron dose: 30.0 e/Å2
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
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