Inhibition of translation by peptide ligands targeting the stem-loop H18 in 16S rRNA

AEI 21

Beatriz Llano-Sotelo, bllano@uic.edu, Dorota Klepacki, klepacki@uic.edu, and Alexander S. Mankin, shura@uic.edu. Center for Pharmaceutical Biotechnology, University of Illinois, (M/C 870) Molecular Biology Research Building, Room 3056 900 South Ashland Avenue Chicago, Chicago, IL 60607-7173
The stem-loop H18 in 16S rRNAp plays a central role in the ribosome-tRNA interactions and in decoding. H18 folds into a pseudoknot whose disruption is detrimental for translation. In an attempt to validate H18 as an antibiotic traget and to identify small ligands capable of binding to this RNA element in the ribosome, we used phage display to select peptides capable of specific binding to H18. A 59-nt hybrid RNA-DNA construct representing H18 of Bacillus anthracis small ribosomal subunit was used as bait for screening of a random heptapeptide phage display library. Several heptapeptides were identified, chemically syntehsized and tested in the E. coli cell-free transcription-translation system. Two of the tested peptides, BLS15 and BLS18, exhibited considerable inhibitory activity with an IC50 of 15 µM, and 137 µM, respectively. The idetified peptides can be used for screening of libraries of synthetic and natural organic compounds for drug leads affecting translation.