EMD-19541
Structure of a yeast 48S-AUC preinitiation complex in closed conformation
EMD-19541
Single-particle3.35 Å
Deposition: 02/02/2024
Map released: 11/09/2024
Last modified: 23/10/2024
Sample Organism:
Kluyveromyces lactis NRRL Y-1140,
Saccharomyces cerevisiae S288C,
Kluyveromyces lactis
Sample: Structure of a yeast 48S-AUC preinitiation complex in closed conformation
Fitted models: 8rw1 (Avg. Q-score: 0.404)
Deposition Authors: Villamayor-Belinchon L , Sharma P , Llacer JL , Hussain T
Sample: Structure of a yeast 48S-AUC preinitiation complex in closed conformation
Fitted models: 8rw1 (Avg. Q-score: 0.404)
Deposition Authors: Villamayor-Belinchon L , Sharma P , Llacer JL , Hussain T
Structural basis of AUC codon discrimination during translation initiation in yeast.
Villamayor-Belinchon L ,
Sharma P ,
Gordiyenko Y,
Llacer JL ,
Hussain T
(2024) Nucleic Acids Res , 52 , 11317 - 11335
(2024) Nucleic Acids Res , 52 , 11317 - 11335
Abstract:
In eukaryotic translation initiation, the 48S preinitiation complex (PIC) scans the 5' untranslated region of mRNAs to search for the cognate start codon (AUG) with assistance from various eukaryotic initiation factors (eIFs). Cognate start codon recognition is precise, rejecting near-cognate codons with a single base difference. However, the structural basis of discrimination of near-cognate start codons was not known. We have captured multiple yeast 48S PICs with a near-cognate AUC codon at the P-site, revealing that the AUC codon induces instability in the codon-anticodon at the P-site, leading to a disordered N-terminal tail of eIF1A. Following eIF1 dissociation, the N-terminal domain of eIF5 fails to occupy the vacant eIF1 position, and eIF2β becomes flexible. Consequently, 48S with an AUC codon is less favourable for initiation. Furthermore, we observe hitherto unreported metastable states of the eIF2-GTP-Met-tRNAMet ternary complex, where the eIF2β helix-turn-helix domain may facilitate eIF5 association by preventing eIF1 rebinding to 48S PIC. Finally, a swivelled head conformation of 48S PIC appears crucial for discriminating incorrect and selection of the correct codon-anticodon pair during translation initiation.
In eukaryotic translation initiation, the 48S preinitiation complex (PIC) scans the 5' untranslated region of mRNAs to search for the cognate start codon (AUG) with assistance from various eukaryotic initiation factors (eIFs). Cognate start codon recognition is precise, rejecting near-cognate codons with a single base difference. However, the structural basis of discrimination of near-cognate start codons was not known. We have captured multiple yeast 48S PICs with a near-cognate AUC codon at the P-site, revealing that the AUC codon induces instability in the codon-anticodon at the P-site, leading to a disordered N-terminal tail of eIF1A. Following eIF1 dissociation, the N-terminal domain of eIF5 fails to occupy the vacant eIF1 position, and eIF2β becomes flexible. Consequently, 48S with an AUC codon is less favourable for initiation. Furthermore, we observe hitherto unreported metastable states of the eIF2-GTP-Met-tRNAMet ternary complex, where the eIF2β helix-turn-helix domain may facilitate eIF5 association by preventing eIF1 rebinding to 48S PIC. Finally, a swivelled head conformation of 48S PIC appears crucial for discriminating incorrect and selection of the correct codon-anticodon pair during translation initiation.