Structural Changes Enable Start Codon Recognition by the Eukaryotic Translation Initiation Complex

By T. Hussain, J. Llácer, I. S. Fernández, Antonio M. Muñoz, Pilar Martin-Marcos, C. Savva, J. Lorsch, A. Hinnebusch, V. Ramakrishnan. 2014

211 citations recorded by the source corpus.

Summary During eukaryotic translation initiation, initiator tRNA does not insert fully into the P decoding site on the 40S ribosomal subunit. This conformation (POUT) is compatible with scanning mRNA for the AUG start codon. Base pairing with AUG is thought to promote isomerization to a more stable conformation (PIN) that arrests scanning and promotes dissociation of eIF1 from the 40S subunit. Here, we present a cryoEM reconstruction of a yeast preinitiation complex at 4.0 Å resolution with initiator tRNA in the PIN state, prior to eIF1 release. The structure reveals stabilization of the codon-anticodon duplex by the N-terminal tail of eIF1A, changes in the structure of eIF1 likely instrumental in its subsequent release, and changes in the conformation of eIF2. The mRNA traverses the entire mRNA cleft and makes connections to the regulatory domain of eIF2α, eIF1A, and ribosomal elements that allow recognition of context nucleotides surrounding the AUG codon.

Subfields: Molecular Biology

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Citations in the corpus

Long-range interdomain communications in eIF5B regulate GTP hydrolysis and translation initiation (2020, methodology): “These conditions have been previously used for other 40S initiation complexes studied by cryo-EM (12, 38), but not for a late intermediate with eIF5B and 60S.”
The Jigsaw Puzzle of mRNA Translation Initiation in Eukaryotes: A Decade of Structures Unraveling the Mechanics of the Process (2018, background): “The resulting 48S initiation complex (IC), in the open POUT conformation in which Met-tRNAi is not fully accommodated in the P site, scans the 5′ region until it encounters the AUG start codon in a suitable initiation context (60, 81).”
Structural Insights into the Mammalian Late-Stage Initiation Complexes (2020, methodology): “The complexes were prepared using a modified version of our approach (Simonetti et al., 2016; seeSTARMethods) that consists of stalling the LS48S IC in RRL using GMP-PNP (a non-hydrolyzable analog of GTP) on the two target cellular mRNAs: mouse histone H4 mRNA (suboptimal Kozak) and human b-globin m”
Structural Insights into the Mechanism of Scanning and Start Codon Recognition in Eukaryotic Translation Initiation. (2017, methodology): “Whereas (archaeal) aIF2adomains1and2 (D1–2) interactwith the tRNA elbow, they are dramatically rearranged in the yeast py48S complexes with D1 contacting the anticodonstem loop (ASL)andD2 interactingwith theD-/T-loopsof tRNAi, slightlydistorting theTloop [20].”
Protein Synthesis Initiation in Eukaryotic Cells. (2018, background): “As described below, cryoelectron microscopy (cryoEM) of partial 48S complexes has provided further insight into Met-tRNAi binding by eIF2 (Hussain et al. 2014; Llacer et al. 2015; Hinnebusch 2017; Jobe et al. 2018).”
Toward a Kinetic Understanding of Eukaryotic Translation. (2018, background): “Such a conformational change may be similar to the recent structural model in which eIF1 adopts an altered conformation whenMettRNAi adopts the accommodated conformation (PIN state described above) (Hussain et al. 2014; Llácer et al. 2015).”