Poster abstracts

Poster number 31 submitted by Cecilia Go

Developing novel antibacterials using cyclic peptide mimics of the protein subunit of bacterial RNase P

Cecilia Go (Dept. of Biochemistry, The Ohio State University, Columbus, Ohio, USA), Krystyna Patora (Dept. of Chemistry, University of Zürich, Zürich, Switzerland), Jitesh Soares and Brian Ahmer (Dept. of Microbiology, The Ohio State University, Columbus, Ohio, USA), John A. Robinson (Dept. of Chemistry, University of Zürich, Zürich, Switzerland), Gabriele Varani (Dept. of Chemistry, University of Washington, Seattle, Washington, USA), Venkat Gopalan (Dept. of Biochemistry, The Ohio State University, Columbus, Ohio, USA)

Abstract:
The increased prevalence of drug-resistant bacteria is a global human health problem. RNA-protein (RNP) complexes, which play a vital role in cellular processes, have merited scrutiny as candidate targets for novel antibacterials. RNase P, a catalytic RNP, is primarily responsible for the Mg²⁺-dependent removal of the 5’ leader sequence in all precursor tRNAs. Despite its essential and conserved function in tRNA biogenesis, the subunit composition of the RNase P holoenzyme varies in the three domains of life. All holoenzymes comprise an essential RNase P RNA (RPR) and a variable number of RNase P Protein (RPP) subunits: one, four, and nine in Bacteria, Archaea, and Eukarya, respectively. We have exploited the striking differences between the structure of RNase P in pathogenic bacteria and their eukaryotic hosts for designing new antibacterials. In this study, we hypothesized that certain synthetic arginine-rich, â-hairpin peptides, designed to disrupt the assembly of viral protein-RNA complexes, would also serve as structural mimics of a highly conserved helix in bacterial RPPs and disrupt bacterial RNase P assembly. Indeed, some of these cyclic peptides exhibited sub-micromolar IC50 values when tested in vitro for their ability to inhibit the ptRNA processing activity of recombinant Escherichia coli RNase P. Moreover, as the RPR and RPP are ~99% identical between the corresponding antibiotic-resistant and -sensitive variants of different pathogenic bacteria, we predicted and confirmed (using Salmonella typhi as a test case) that the MIC values (determined to be ~ 1 mM) for our most potent inhibitor are indistinguishable between resistant and sensitive strains. This active peptide also had no effect on growth of HeLa cells. Ongoing directions include determining the inhibitor’s mechanism of action and proving that cessation of bacterial growth in culture stems from decreased RNase P activity in vivo.

Keywords: RNase P