Translation initiation by the Kozak mRNA sequence is based on a conformational readout on the ribosome
Abstract
The recognition mechanism of Kozak mRNA, typically comprising purines in the -3 and +4 positions flanking the AUG start codon, has remained enigmatic for decades. To address this fundamental function in eukaryotes during translation initiation, we analysed several cryo-EM structures of human 48S preinitiation complexes with mRNA sequences differing in Kozak activity revealing distinct modes of recognition. The pre-codon triplet forms a fan-like intercalation into the 18S ribosomal RNA (rRNA), while a -3 pyrimidine destabilizes ternary complex positioning. Specificity towards the +4 purine is achieved beyond a single residue recognition by mutual conformational adaptations of eIF1A, mRNA and rRNA that involve the insertion of a reading head in which decoding residue A1825 (rRNA) stacks with the A-site codon to stabilize the fully accommodated state. Hence, instead of relying on base pairing as in bacteria, the specific recognition of the Kozak sequence on eukaryotic ribosomes is based on an induced-fit mechanism that triggers a conformational readout of the mRNA.
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BibTeX
@article{loeffelholz2026translation,
title = {{Translation initiation by the Kozak mRNA sequence is based on a conformational readout on the ribosome}},
author = {Ottilie von Loeffelholz and Charles Barchet and Samuel Holvec and Aida Abou Ramadan and Cristina Protuc and Isabelle Hazemann and Bruno Klaholz},
journal = {Nature Communications},
year = {2026},
month = jul,
doi = {10.1038/s41467-026-73969-2},
url = {https://hal.science/hal-05761405v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - Translation initiation by the Kozak mRNA sequence is based on a conformational readout on the ribosome
AU - Ottilie von Loeffelholz
AU - Charles Barchet
AU - Samuel Holvec
AU - Aida Abou Ramadan
AU - Cristina Protuc
AU - Isabelle Hazemann
AU - Bruno Klaholz
PY - 2026
DA - 2026/07/08
JO - Nature Communications
DO - 10.1038/s41467-026-73969-2
UR - https://hal.science/hal-05761405v1
AB - The recognition mechanism of Kozak mRNA, typically comprising purines in the -3 and +4 positions flanking the AUG start codon, has remained enigmatic for decades. To address this fundamental function in eukaryotes during translation initiation, we analysed several cryo-EM structures of human 48S preinitiation complexes with mRNA sequences differing in Kozak activity revealing distinct modes of recognition. The pre-codon triplet forms a fan-like intercalation into the 18S ribosomal RNA (rRNA), while a -3 pyrimidine destabilizes ternary complex positioning. Specificity towards the +4 purine is achieved beyond a single residue recognition by mutual conformational adaptations of eIF1A, mRNA and rRNA that involve the insertion of a reading head in which decoding residue A1825 (rRNA) stacks with the A-site codon to stabilize the fully accommodated state. Hence, instead of relying on base pairing as in bacteria, the specific recognition of the Kozak sequence on eukaryotic ribosomes is based on an induced-fit mechanism that triggers a conformational readout of the mRNA.
SN - 2041-1723
SN - 2041-1723
ER -