In vitro selection of a viomycin-binding RNA pseudoknot

Background: The peptide antibiotic viomycin inhibits ribosomal protein synthesis, group I intron self-splicing and self-cleavage of the human hepatitis delta virus ribozyme. To understand the molecular basis of RNA binding and recognition by viomycin, we isolated a variety of novel viomycin-binding RNA molecules using in vitro selection. Results: More than 90% of the selected RNA molecules shared one continuous highly conserved region of 14 nucleotides. Mutational analyses, structural probing, together with footprinting experiments by chemical modification, and Pb2+-induced cleavage showed that this conserved sequence harbours the antibiotic-binding site and forms a stem-loop structure, Moreover, the loop is engaged in a long-range interaction forming a pseudoknot. Conclusions: A comparison between the novel viomycin-binding motif and the natural RNA target sites for viomycin showed that all these segments forma pseudoknot al the antibiotic-binding site. We therefore conclude that this peptide antibiotic has a strong selectivity for particular RNA pseudoknots.