Journal: Cell / Year: 2013 Title: Structure of the mammalian ribosomal 43S preinitiation complex bound to the scanning factor DHX29. Authors: Yaser Hashem / Amedee des Georges / Vidya Dhote / Robert Langlois / Hstau Y Liao / Robert A Grassucci / Christopher U T Hellen / Tatyana V Pestova / Joachim Frank / Abstract: Eukaryotic translation initiation begins with assembly of a 43S preinitiation complex. First, methionylated initiator methionine transfer RNA (Met-tRNAi(Met)), eukaryotic initiation factor (eIF) 2, ...Eukaryotic translation initiation begins with assembly of a 43S preinitiation complex. First, methionylated initiator methionine transfer RNA (Met-tRNAi(Met)), eukaryotic initiation factor (eIF) 2, and guanosine triphosphate form a ternary complex (TC). The TC, eIF3, eIF1, and eIF1A cooperatively bind to the 40S subunit, yielding the 43S preinitiation complex, which is ready to attach to messenger RNA (mRNA) and start scanning to the initiation codon. Scanning on structured mRNAs additionally requires DHX29, a DExH-box protein that also binds directly to the 40S subunit. Here, we present a cryo-electron microscopy structure of the mammalian DHX29-bound 43S complex at 11.6 Å resolution. It reveals that eIF2 interacts with the 40S subunit via its α subunit and supports Met-tRNAi(Met) in an unexpected P/I orientation (eP/I). The structural core of eIF3 resides on the back of the 40S subunit, establishing two principal points of contact, whereas DHX29 binds around helix 16. The structure provides insights into eukaryote-specific aspects of translation, including the mechanism of action of DHX29.
History
Deposition
May 1, 2013
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Header (metadata) release
May 22, 2013
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Map release
Jun 5, 2013
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Update
Jun 5, 2013
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Current status
Jun 5, 2013
Processing site: RCSB / Status: Released
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Structure visualization
Movie
Surface view with section colored by density value
Entire : Cryo-electron microscopy structure of the mammalian 43S preinitia...
Entire
Name: Cryo-electron microscopy structure of the mammalian 43S preinitiation complex bound to DHX29
Components
Sample: Cryo-electron microscopy structure of the mammalian 43S preinitiation complex bound to DHX29
Complex: eukaryotic small ribosomal subunit
Protein or peptide: eukaryotic initiation factor 3
Protein or peptide: eukaryotic initiation factor 2
Protein or peptide: eukaryotic initiation factor 1
Protein or peptide: eukaryotic initiation factor 1A
Protein or peptide: DHX29
RNA: Transfer RNA
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Supramolecule #1000: Cryo-electron microscopy structure of the mammalian 43S preinitia...
Supramolecule
Name: Cryo-electron microscopy structure of the mammalian 43S preinitiation complex bound to DHX29 type: sample / ID: 1000 Oligomeric state: One 40S binds one eIF3, one eIF2, one Met-tRNAiMet, and one DHX29 Number unique components: 5
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Supramolecule #1: eukaryotic small ribosomal subunit
Cryogen name: ETHANE / Chamber humidity: 100 % / Chamber temperature: 120 K / Instrument: FEI VITROBOT MARK II / Method: Blot for seconds before plunging
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Electron microscopy
Microscope
FEI TECNAI 20
Temperature
Average: 110 K
Date
Nov 1, 2012
Image recording
Category: CCD / Film or detector model: GATAN ULTRASCAN 4000 (4k x 4k) / Number real images: 8000 / Average electron dose: 12 e/Å2 / Bits/pixel: 32
Electron beam
Acceleration voltage: 110 kV / Electron source: FIELD EMISSION GUN
The particles of this reconstruction were obtained after particle sorting using Relion
CTF correction
Details: Each particle
Final reconstruction
Algorithm: OTHER / Resolution.type: BY AUTHOR / Resolution: 11.6 Å / Resolution method: OTHER / Software - Name: Spider, Relion / Number images used: 29000
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