Download MendeleyCompact IF2 allows initiator tRNA accommodation into the P site and gates the ribosome to elongation.
Basu, R.S., Sherman, M.B., Gagnon, M.G.(2022) Nat Commun 13: 3388-3388
- PubMed: 35697706
- DOI: https://doi.org/10.1038/s41467-022-31129-2
- Primary Citation of Related Structures:
7UIU - PubMed Abstract:
During translation initiation, initiation factor 2 (IF2) holds initiator transfer RNA (fMet-tRNA i fMet ) in a specific orientation in the peptidyl (P) site of the ribosome. Upon subunit joining IF2 hydrolyzes GTP and, concomitant with inorganic phosphate (P i ) release, changes conformation facilitating fMet-tRNA i fMet accommodation into the P site and transition of the 70 S ribosome initiation complex (70S-IC) to an elongation-competent ribosome. The mechanism by which IF2 separates from initiator tRNA at the end of translation initiation remains elusive. Here, we report cryo-electron microscopy (cryo-EM) structures of the 70S-IC from Pseudomonas aeruginosa bound to compact IF2-GDP and initiator tRNA. Relative to GTP-bound IF2, rotation of the switch 2 α-helix in the G-domain bound to GDP unlocks a cascade of large-domain movements in IF2 that propagate to the distal tRNA-binding domain C2. The C2-domain relocates 35 angstroms away from tRNA, explaining how IF2 makes way for fMet-tRNA i fMet accommodation into the P site. Our findings provide the basis by which IF2 gates the ribosome to the elongation phase.
Organizational Affiliation:
Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, 77555, USA.
