title: Specific interaction between EF-G and RRF and its implication for GTP-dependent ribosome splitting into subunits.
abstract: After termination of protein synthesis, the bacterial ribosome is split into its 30S and 50S subunits by the action of ribosome recycling factor (RRF) and elongation factor G (EF-G) in a guanosine 5'-triphosphate (GTP)-hydrolysis-dependent manner. Based on a previous cryo-electron microscopy study of ribosomal complexes, we have proposed that the binding of EF-G to an RRF-containing posttermination ribosome triggers an interdomain rotation of RRF, which destabilizes two strong intersubunit bridges (B2a and B3) and, ultimately, separates the two subunits. Here, we present a 9-A (Fourier shell correlation cutoff of 0.5) cryo-electron microscopy map of a 50S x EF-G x guanosine 5'-[(betagamma)-imido]triphosphate x RRF complex and a quasi-atomic model derived from it, showing the interaction between EF-G and RRF on the 50S subunit in the presence of the noncleavable GTP analogue guanosine 5'-[(betagamma)-imido]triphosphate. The detailed information in this model and a comparative analysis of EF-G structures in various nucleotide- and ribosome-bound states show how rotation of the RRF head domain may be triggered by various domains of EF-G. For validation of our structural model, all known mutations in EF-G and RRF that relate to ribosome recycling have been taken into account. More importantly, our results indicate a substantial conformational change in the Switch I region of EF-G, suggesting that a conformational signal transduction mechanism, similar to that employed in transfer RNA translocation on the ribosome by EF-G, translates a large-scale movement of EF-G's domain IV, induced by GTP hydrolysis, into the domain rotation of RRF that eventually splits the ribosome into subunits.
authors.affiliation: Howard Hughes Medical Institute, Wadsworth Center, Empire State Plaza, Albany, NY 12201-0509, USA.
authors.forename: Ning
authors.initials: N
authors.lastname: Gao
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Zavialov
authors.forename: Måns
authors.initials: M
authors.lastname: Ehrenberg
authors.forename: Joachim
authors.initials: J
authors.lastname: Frank
mesh_terms: D000595:Amino Acid Sequence; D020285:Cryoelectron Microscopy; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006868:Hydrolysis; D008969:Molecular Sequence Data; D020653:Peptide Elongation Factor G / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D012333:RNA, Messenger / Q000235:genetics; D012269:Ribosomal Proteins / Q000737:chemistry / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*; D012542:Scattering, Radiation; D017386:Sequence Homology, Amino Acid
chemical_list: D020653:Peptide Elongation Factor G; D012333:RNA, Messenger; D012269:Ribosomal Proteins; C087267:ribosome releasing factor; D006160:Guanosine Triphosphate