title: UV-induced modifications in the peptidyl transferase loop of 23S rRNA dependent on binding of the streptogramin B antibiotic, pristinamycin IA.
abstract: The naturally occurring streptogramin B antibiotic, pristinamycin IA, which inhibits peptide elongation, can produce two modifications in 23S rRNA when bound to the Escherichia coli 70S ribosome and irradiated at 365 nm. Both drug-induced effects map to highly conserved nucleotides within the functionally important peptidyl transferase loop of 23S rRNA at positions m2A2503/psi2504 and G2061/A2062. The modification yields are influenced strongly, and differentially, by P-site-bound tRNA and strongly by some of the peptidyl transferase antibiotics tested, with chloramphenicol producing a shift in the latter modification to A2062/C2063. Pristinamycin IA can also produce a modification on binding to deproteinized, mature 23S rRNA, at position U2500/C2501. The same modification occurs on an approximately 37-nt fragment, encompassing positions approximately 2496-2532 of the peptidyl transferase loop that was excised from the mature rRNA using RNAse H. In contrast, no antibiotic-induced effects were observed on in vitro T7 transcripts of full-length 23S rRNA, domain V, or on a fragment extending from positions approximately 2496-2566, which indicates that one or more posttranscriptional modifications within the sequence Cm-C-U-C-G-m2A-psi-G2505 are important for pristinamycin IA binding and/or the antibiotic-dependent modification of 23S rRNA.
authors: RNA Regulation Centre, Institute of Molecular Biology, University of Copenhagen, Denmark.
authors: B T
authors: BT
authors: Porse
authors: S V
authors: SV
authors: Kirillov
authors: M J
authors: MJ
authors: Awayez
authors: R A
authors: RA
authors: Garrett
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D004926:Escherichia coli / Q000235:genetics*; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010458:Peptidyl Transferases / Q000235:genetics* / Q000528:radiation effects; D012323:RNA Processing, Post-Transcriptional / Q000528:radiation effects; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism; D012338:RNA, Ribosomal, 23S / Q000235:genetics*; D012343:RNA, Transfer / Q000235:genetics / Q000378:metabolism; D016914:Ribonuclease H / Q000378:metabolism; D014466:Ultraviolet Rays; D014769:Virginiamycin / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D012329:RNA, Bacterial; D012338:RNA, Ribosomal, 23S; D014769:Virginiamycin; D012343:RNA, Transfer; D010458:Peptidyl Transferases; D016914:Ribonuclease H