title: Protection of ribosomal RNA from kethoxal in polyribosomes. Implication of specific sites in ribosome function.
abstract: In an attempt to probe the topography of 5 S, 16 S and 23 S RNAs in a functionally engaged ribosome, polysomes were probed using the structure-sensitive, guanine-specific reagent kethoxal. Reactivities of guanine residues at 38 specific ribosomal RNA sites in polysomes were compared with their corresponding reactivities in vacant 70 S ribosomes. No polysome-specific protection was seen for 5 S RNA. In 16 S RNA, positions 530, 693 or 1079, 966, 1338 and 1517 showed protection in polysomes; all of these sites have highly conserved primary and secondary structures, and include several methylated nucleotides. In 23 S RNA, polysome protection is seen at positions 277, 1071, 1475 or 2112, 2116 and 2751. We attribute polysome-specific protection either to direct contact of transfer RNA and/or messenger RNA with the protected sites or to tRNA and/or mRNA-induced changes in ribosome conformation involving the protected sites.
mesh_terms: D000447:Aldehydes / Q000494:pharmacology*; D001483:Base Sequence; D001665:Binding Sites / Q000187:drug effects; D002074:Butanones; D004590:Electrophoresis, Paper; D006147:Guanine / Q000032:analysis; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000032:analysis; D011132:Polyribosomes / Q000187:drug effects* / Q000378:metabolism; D012335:RNA, Ribosomal / Q000378:metabolism*; D012343:RNA, Transfer / Q000032:analysis
chemical_list: D000447:Aldehydes; D002074:Butanones; D009841:Oligonucleotides; D012335:RNA, Ribosomal; D006147:Guanine; D012343:RNA, Transfer; C005135:kethoxal