Cryo-EM study of start codon selection during archaeal translation initiation.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 27819266.
- Also identified by DOI 10.1038/ncomms13366 and PMC identifier 5103072.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
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<sub>i</sub><sup>Met</sup>) 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.
Medical subject headings
- Archaea
- Archaeal Proteins
- Peptide Chain Initiation, Translational
- Peptide Initiation Factors
- Ribosome Subunits, Small, Archaeal