Open AccessCryo-EM study of start codon selection during archaeal translation initiation
Author(s) -
PierreDamien Coureux,
Christine LazennecSchurdevin,
Auriane Monestier,
Éric Larquet,
Lionel Cladière,
Bruno P. Klaholz,
Emmanuelle Schmitt,
Yves Mechulam
Publication year - 2016
Publication title -
nature communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.559
H-Index - 365
ISSN - 2041-1723
DOI - 10.1038/ncomms13366
Subject(s) - transfer rna , start codon , eif2 , biology , translation (biology) , genetics , ribosome , p site , eukaryotic translation , initiation factor , computational biology , messenger rna , rna , gene
Eukaryotic and archaeal translation initiation complexes have a common structural core comprising e/aIF1, e/aIF1A, the ternary complex (TC, e/aIF2-GTP-Met-tRNA i Met ) and mRNA bound to the small ribosomal subunit. e/aIF2 plays a crucial role in this process but how this factor controls start codon selection remains unclear. Here, we present cryo-EM structures of the full archaeal 30S initiation complex showing two conformational states of the TC. In the first state, the TC is bound to the ribosome in a relaxed conformation with the tRNA oriented out of the P site. In the second state, the tRNA is accommodated within the peptidyl (P) site and the TC becomes constrained. This constraint is compensated by codon/anticodon base pairing, whereas in the absence of a start codon, aIF2 contributes to swing out the tRNA. This spring force concept highlights a mechanism of codon/anticodon probing by the initiator tRNA directly assisted by aIF2.