title: Changes in the conformation of 5S rRNA cause alterations in principal functions of the ribosomal nanomachine.
abstract: 5S rRNA is an integral component of the large ribosomal subunit in virtually all living organisms. Polyamine binding to 5S rRNA was investigated by cross-linking of N1-azidobenzamidino (ABA)-spermine to naked 5S rRNA or 50S ribosomal subunits and whole ribosomes from Escherichia coli cells. ABA-spermine cross-linking sites were kinetically measured and their positions in 5S rRNA were localized by primer extension analysis. Helices III and V, and loops A, C, D and E in naked 5S rRNA were found to be preferred polyamine binding sites. When 50S ribosomal subunits or poly(U)-programmed 70S ribosomes bearing tRNA(Phe) at the E-site and AcPhe-tRNA at the P-site were targeted, the susceptibility of 5S rRNA to ABA-spermine was greatly reduced. Regardless of 5S rRNA assembly status, binding of spermine induced significant changes in the 5S rRNA conformation; loop A adopted an apparent 'loosening' of its structure, while loops C, D, E and helices III and V achieved a more compact folding. Poly(U)-programmed 70S ribosomes possessing 5S rRNA cross-linked with spermine were more efficient than control ribosomes in tRNA binding, peptidyl transferase activity and translocation. Our results support the notion that 5S rRNA serves as a signal transducer between regions of 23S rRNA responsible for principal ribosomal functions.
authors.affiliation: Laboratory of Biochemistry, School of Medicine, University of Patras, GR-26500 Patras, Greece.
authors.forename: Ekaterini C
authors.initials: EC
authors.lastname: Kouvela
authors.forename: George V
authors.initials: GV
authors.lastname: Gerbanas
authors.forename: Maria A
authors.initials: MA
authors.lastname: Xaplanteri
authors.forename: Alexandros D
authors.initials: AD
authors.lastname: Petropoulos
authors.forename: George P
authors.initials: GP
authors.lastname: Dinos
authors.forename: Dimitrios L
authors.initials: DL
authors.lastname: Kalpaxis
mesh_terms: D001386:Azides / Q000737:chemistry; D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010458:Peptidyl Transferases / Q000378:metabolism; D019920:Photoaffinity Labels; D011072:Poly U / Q000378:metabolism; D012329:RNA, Bacterial / Q000737:chemistry; D012341:RNA, Ribosomal, 5S / Q000737:chemistry*; D012346:RNA, Transfer, Amino Acyl / Q000378:metabolism; D012270:Ribosomes / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism*; D013096:Spermine / Q000031:analogs & derivatives / Q000737:chemistry
chemical_list: D001386:Azides; D019920:Photoaffinity Labels; D012329:RNA, Bacterial; D012341:RNA, Ribosomal, 5S; D012346:RNA, Transfer, Amino Acyl; C006383:tRNA, N-acetylphenylalanine-; C068638:N(1)-(azidobenzamidino)spermine; D011072:Poly U; D013096:Spermine; D010458:Peptidyl Transferases