Identification of an RNA-Protein Bridge Spanning the Ribosomal Subunit Interface

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Culver, Gloria | Cate, Jamie | Yusupova, G. Zh. | Yusupov, Marat | Noller, Harry

Edité par CCSD ; American Association for the Advancement of Science (AAAS) -

International audience. The 7.8 angstrom crystal structure of the 70 S ribosome reveals a discrete double-helical bridge (B4) that projects from the 50 S subunit, making contact with the 30 S 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 23 S ribosomal RNA, one of the known sites in 23 S ribosomal RNA that are footprinted by the 30 S subunit. Reconstitution studies show that protection of the 715 loop, but none of the other 30 S -dependent protections, is correlated with the presence of S15 in the 30 S subunit. The 715 loop is specifically protected by binding free S15 to 50 S 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.

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