title: Identification of an RNA-protein bridge spanning the ribosomal subunit interface.
abstract: The 7.8 angstrom crystal structure of the 70S ribosome reveals a discrete double-helical bridge (B4) that projects from the 50S subunit, making contact with the 30S subunit. Preliminary modeling studies localized its contact site, near the bottom of the platform, to the binding site for ribosomal protein S15. Directed hydroxyl radical probing from iron(II) tethered to S15 specifically cleaved nucleotides in the 715 loop of domain II of 23S ribosomal RNA, one of the known sites in 23S ribosomal RNA that are footprinted by the 30S subunit. Reconstitution studies show that protection of the 715 loop, but none of the other 30S-dependent protections, is correlated with the presence of S15 in the 30S subunit. The 715 loop is specifically protected by binding free S15 to 50S subunits. Moreover, the previously determined structure of a homologous stem-loop from U2 small nuclear RNA fits closely to the electron density of the bridge.
authors.affiliation: Center for Molecular Biology of RNA, Sinsheimer Laboratories, University of California, Santa Cruz, CA 95064, USA.
authors.forename: G M
authors.initials: GM
authors.lastname: Culver
authors.forename: J H
authors.initials: JH
authors.lastname: Cate
authors.forename: G Z
authors.initials: GZ
authors.lastname: Yusupova
authors.forename: M M
authors.initials: MM
authors.lastname: Yusupov
authors.forename: H F
authors.initials: HF
authors.lastname: Noller
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000737:chemistry; D017665:Hydroxyl Radical; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D012329:RNA, Bacterial / Q000737:chemistry* / Q000378:metabolism; D012338:RNA, Ribosomal, 23S / Q000737:chemistry* / Q000378:metabolism; D012342:RNA, Small Nuclear / Q000737:chemistry / Q000378:metabolism; D012269:Ribosomal Proteins / Q000737:chemistry / Q000378:metabolism*; D012270:Ribosomes / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D016963:Thermus thermophilus / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D012329:RNA, Bacterial; D012338:RNA, Ribosomal, 23S; D012342:RNA, Small Nuclear; D012269:Ribosomal Proteins; C036004:ribosomal protein S15; D017665:Hydroxyl Radical