Unmasking IF2's moves at the start of translation
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| Year of publication | 2025 |
| Type | Conference abstract |
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| Description | Bacterial translation initiation is a crucial step in gene expression. It starts with the recruitment of the initiator tRNA to the P-site of the 30S ribosomal subunit, followed by joining of the 50S subunit to form the 70S ribosome. Within the 30S initiation complex (IC), initiation factor 1 (IF1) occupies the A-site, while initiation factor 2 (IF2), a GTPase, promotes subunit joining by facilitating docking of the 50S subunit. This transition to the 70S IC is accompanied by GTP hydrolysis and subsequent dissociation of IF2, ultimately yielding an elongation-competent 70S ribosome. While conformational rearrangements of IF2 have been implicated in its release, the role of its N-terminal domain and the exact timing of IF1 departure remain unclear. Here, we used the ?-form of IF2 (E. coli) in combination with time-resolved cryo-EM to address the open questions in bacterial translation initiation. Our results reveal that IF1 dissociates from the 30S subunit prior to 70S IC formation and highlight the stabilizing role of IF2’s N-terminal domain on the 30S subunit during the initiation phase. Additionally, we captured conformational changes in IF2 following GTP hydrolysis, providing a detailed structural view of the molecular events that govern the transition from translation initiation to elongation. |
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