title: The real-time path of translation factor IF3 onto and off the ribosome.
abstract: Translation initiation factor IF3 is an essential bacterial protein, consisting of two domains (IF3C and IF3N) separated by a linker, which interferes with ribosomal subunit association, promotes codon-anticodon interaction in the P site, and ensures translation initiation fidelity. Using time-resolved chemical probing, we followed the dynamic binding path of IF3 on the 30S subunit and its release upon 30S-50S association. During binding, IF3 first contacts the platform (near G700) of the 30S subunit with the C domain and then the P-decoding region (near A790) with its N domain. At equilibrium, attained within less than a second, both sites are protected, but before reaching binding equilibrium, IF3 causes additional transient perturbations of both the platform edge and the solvent side of the subunit. Upon 30S-50S association, IF3 dissociates concomitantly with the establishment of the 30S-50S bridges, following the reverse path of its binding with the IF3N-A790 interaction being lost before the IF3C-G700 interaction.
authors.affiliation: Laboratory of Genetics, Department of Biology, University of Camerino, 62032 Camerino, MC, Italy.
authors.forename: Attilio
authors.initials: A
authors.lastname: Fabbretti
authors.forename: Cynthia L
authors.initials: CL
authors.lastname: Pon
authors.forename: Scott P
authors.initials: SP
authors.lastname: Hennelly
authors.forename: Walter E
authors.initials: WE
authors.lastname: Hill
authors.forename: J Stephen
authors.initials: JS
authors.lastname: Lodmell
authors.forename: Claudio O
authors.initials: CO
authors.lastname: Gualerzi
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D039665:Prokaryotic Initiation Factor-3 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012336:RNA, Ribosomal, 16S / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000737:chemistry / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D039665:Prokaryotic Initiation Factor-3; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D011994:Recombinant Proteins