title: The ribosome modulation factor (RMF) binding site on the 100S ribosome of Escherichia coli.
abstract: During the stationary growth phase, Escherichia coli 70S ribosomes are converted to 100S ribosomes, and translational activity is lost. This conversion is caused by the binding of the ribosome modulation factor (RMF) to 70S ribosomes. In order to elucidate the mechanisms by which 100S ribosomes form and translational inactivation occurs, the shape of the 100S ribosome and the RMF ribosomal binding site were investigated by electron microscopy and protein-protein cross-linking, respectively. We show that (i) the 100S ribosome is formed by the dimerization of two 70S ribosomes mediated by face-to-face contacts between their constituent 30S subunits, and (ii) RMF binds near the ribosomal proteins S13, L13, and L2. The positions of these proteins indicate that the RMF binding site is near the peptidyl transferase center or the P site (peptidyl-tRNA binding site). These observations are consistent with the translational inactivation of the ribosome by RMF binding. After the "Recycling" stage, ribosomes can readily proceed to the "Initiation" stage during exponential growth, but during stationary phase, the majority of 70S ribosomes are stored as 100S ribosomes and are translationally inactive. We suggest that this conversion of 70S to 100S ribosomes represents a newly identified stage of the ribosomal cycle in stationary phase cells, and we have termed it the "Hibernation" stage.
authors.affiliation: Department of Physics, Osaka Medical College, Takatsuki, Osaka, 569-8686, Japan. yhide@art.osaka-med.ac.jp
authors.forename: Hideji
authors.initials: H
authors.lastname: Yoshida
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Maki
authors.forename: Hisako
authors.initials: H
authors.lastname: Kato
authors.forename: Hisao
authors.initials: H
authors.lastname: Fujisawa
authors.forename: Kaori
authors.initials: K
authors.lastname: Izutsu
authors.forename: Chieko
authors.initials: C
authors.lastname: Wada
authors.forename: Akira
authors.initials: A
authors.lastname: Wada
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D003432:Cross-Linking Reagents / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D007096:Imidoesters / Q000378:metabolism; D008958:Models, Molecular; D014176:Protein Biosynthesis; D020836:Protein Structure, Quaternary; D012269:Ribosomal Proteins / Q000378:metabolism*; D012270:Ribosomes / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D001426:Bacterial Proteins; D003432:Cross-Linking Reagents; D029968:Escherichia coli Proteins; D007096:Imidoesters; D012269:Ribosomal Proteins; C063545:ribosome modulation factor, E coli; C005905:methyl 4-mercaptobutyrimidate