Journal: Mol Cell / Year: 2015 Title: Conformational Differences between Open and Closed States of the Eukaryotic Translation Initiation Complex. Authors: Jose L Llácer / Tanweer Hussain / Laura Marler / Colin Echeverría Aitken / Anil Thakur / Jon R Lorsch / Alan G Hinnebusch / V Ramakrishnan / Abstract: Translation initiation in eukaryotes begins with the formation of a pre-initiation complex (PIC) containing the 40S ribosomal subunit, eIF1, eIF1A, eIF3, ternary complex (eIF2-GTP-Met-tRNAi), and ...Translation initiation in eukaryotes begins with the formation of a pre-initiation complex (PIC) containing the 40S ribosomal subunit, eIF1, eIF1A, eIF3, ternary complex (eIF2-GTP-Met-tRNAi), and eIF5. The PIC, in an open conformation, attaches to the 5' end of the mRNA and scans to locate the start codon, whereupon it closes to arrest scanning. We present single particle cryo-electron microscopy (cryo-EM) reconstructions of 48S PICs from yeast in these open and closed states, at 6.0 Å and 4.9 Å, respectively. These reconstructions show eIF2β as well as a configuration of eIF3 that appears to encircle the 40S, occupying part of the subunit interface. Comparison of the complexes reveals a large conformational change in the 40S head from an open mRNA latch conformation to a closed one that constricts the mRNA entry channel and narrows the P site to enclose tRNAi, thus elucidating key events in start codon recognition.
History
Deposition
Jun 16, 2015
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Header (metadata) release
Jul 15, 2015
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Map release
Aug 5, 2015
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Update
Aug 19, 2015
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Current status
Aug 19, 2015
Processing site: PDBe / Status: Released
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Structure visualization
Movie
Surface view with section colored by density value
Details: Quantifoil R2/2 400 mesh copper grids with 4-5 nm thin carbon on top
Vitrification
Cryogen name: ETHANE / Chamber humidity: 100 % / Chamber temperature: 120 K / Instrument: FEI VITROBOT MARK I / Timed resolved state: 30 second incubation time / Method: Blot for 2.5-3 seconds before plunging
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Electron microscopy
Microscope
FEI TITAN KRIOS
Alignment procedure
Legacy - Astigmatism: Objective lens astigmatism was corrected at 59,000 times magnification
Details
Complete dataset was collected in 2 non-consecutive sessions
Date
Apr 28, 2014
Image recording
Category: CCD / Film or detector model: FEI FALCON II (4k x 4k) / Number real images: 2056 / Average electron dose: 27 e/Å2 Details: Complete dataset was collected in 2 non-consecutive sessions
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
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