INTERACTION OF TETRACYCLINE WITH RNA - PHOTOINCORPORATION INTO RIBOSOMAL-RNA OF ESCHERICHIA-COLI

Photolysis of [H-3]tetracycline in the presence of Escherichia coli ri bosomes results in an approximately 1:1 ratio of labelling ribosomal p roteins and RNAs. In this work we characterize crosslinks to both 16S and 23S RNAs. Previously, the main target of photoincorporation of [3H ]tetracycline into ribosomal proteins was shown to be S7, which is als o part of the one strong binding site of tetracycline on the 30S subun it, The crosslinks on 23S RNA map exclusively to the central loop of d omain V (G2505, G2576 and G2608) which is part of the peptidyl transfe rase region, However, experiments performed with chimeric ribosomal su bunits demonstrate that peptidyltransferase activity is not affected b y tetracycline crosslinked solely to the 50S subunits. Three different positions are labelled on the 16S RNA, G693, G1300 and G1338. The pos itions of these crosslinked nucleotides correlate well with footprints on the 16S RNA produced either by tRNA or the protein S7, This sugges ts that the nucleotides are labelled by tetracycline behind to the str ong binding site on the 30S subunit, In addition, our results demonstr ate that the well known inhibition of tRNA binding to the A-site is so lely due to tetracycline crosslinked to 30S subunits and furthermore s uggest that interactions of the antibiotic with 16S RNA might be invol ved in its mode of action.