Large-Scale Movements of IF3 and tRNA during Bacterial Translation Initiation.
In bacterial translational initiation, three initiation factors (IFs 1-3) enable the selection of initiator tRNA and the start codon in the P site of the 30S ribosomal subunit. Here, we report 11 single-particle cryo-electron microscopy (cryoEM) reconstructions of the complex of bacterial 30S subunit with initiator tRNA, mRNA, and IFs 1-3, representing different steps along the initiation pathway. IF1 provides key anchoring points for IF2 and IF3, thereby enhancing their activities. IF2 positions a domain in an extended conformation appropriate for capturing the formylmethionyl moiety charged on tRNA. IF3 and tRNA undergo large conformational changes to facilitate the accommodation of the formylmethionyl-tRNA (fMet-tRNA(fMet)) into the P site for start codon recognition.
MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK.
Tanweer
T
Hussain
MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK.
Jose L
JL
Llácer
MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK; Department of Biochemistry and Molecular Genetics, University of Colorado Denver School of Medicine, Aurora, CO 80045, USA.
Brian T
BT
Wimberly
Department of Biochemistry and Molecular Genetics, University of Colorado Denver School of Medicine, Aurora, CO 80045, USA; RNA BioScience Initiative, University of Colorado Denver School of Medicine, Aurora, CO 80045, USA.
Jeffrey S
JS
Kieft
MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK. Electronic address: ramak@mrc-lmb.cam.ac.uk.
V
V
Ramakrishnan
D018387:Codon, Initiator; D020285:Cryoelectron Microscopy; D003461:Crystallography; D010442:Peptide Chain Initiation, Translational; D039665:Prokaryotic Initiation Factor-3 / Q000737:chemistry*; D011487:Protein Conformation; D012333:RNA, Messenger / Q000737:chemistry*; D012358:RNA, Transfer, Met / Q000737:chemistry*; D054680:Ribosome Subunits, Small, Bacterial / Q000737:chemistry*; D016963:Thermus thermophilus / Q000235:genetics / Q000378:metabolism*
D018387:Codon, Initiator; D039665:Prokaryotic Initiation Factor-3; D012333:RNA, Messenger; D012358:RNA, Transfer, Met; C089238:fMet-tRNA(fMet); C024988:tRNA, formylmethionine-
IF1; IF2; IF3; cryo-EM; fMet-tRNA; initiation; ribosome; start codon; structures; translation
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