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Developing Antibacterials Using Cyclic Peptide Mimics of The Protein Subunit of Bacterial RNase P

Go, Cecilia S.

Abstract Details

2010, Master of Science, Ohio State University, Biochemistry.
The increased prevalence of drug-resistant bacteria is a global human health problem. RNA-protein (RNP) complexes, which play a vital role in various 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 in all precursor tRNAs (pre-tRNAs). Despite its essential and conserved primary function in tRNA biogenesis, the subunit composition of the RNase P holoenzyme varies in the three domains of life. All RNase P holoenzymes comprise an essential RNase P RNA (RPR) and a variable number of RNase P Protein (RPP) subunits: one in Bacteria, and at least four and nine in Archaea, and Eukarya, respectively. Towards design of new antibacterials, we have exploited the striking differences between the structure of RNase P in pathogenic bacteria and their eukaryotic hosts. In this study, we hypothesized that certain synthetic Arg-rich, β-hairpin peptides, previously designed to disrupt the assembly of viral protein-RNA complexes, would also serve as structural mimics of a highly conserved, Arg-rich helix in bacterial RPP and disrupt bacterial RNase P assembly. Indeed, some of these cyclic peptides exhibited low-micromolar MIC (Minimal Inhibitory Concentration) values when tested for their ability to inhibit the growth of Salmonella enterica serovar Typhimurium strain 14028 (hereafter referred as S. Typhimurium 14028). While these peptides consist of similar number of Arg residues, their inhibitory potency is probably a reflection of differences in their amino acid sequences. This selectivity highlights the importance of sequence/structure over number of charges. When crude extracts prepared from S. Typhimurium 14028 cells grown in the presence of P17 (a cyclic peptide, which exhibits a low-micromolar MIC value) were tested for pre-tRNA processing, we observed a three-fold decrease in RNase P activity. Northern analysis confirmed pre-tRNAGly and pre-tRNATyr accumulation, indicating that the inhibition of the cell growth is attributable (at least in part) to 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 S. Typhi as a test case that the MIC values (determined to be ~ 1 μM) for our most potent peptide inhibitor are indistinguishable between resistant and sensitive strains. This active peptide also had no effect on growth of HeLa cells. Given the potency and promise of these peptides as antibacterials, it would be of interest to understand their mechanism of action and the means by which they are transported into the bacterial cell.
Venkat Gopalan (Advisor)
Edward Behrman (Committee Member)
Brian Ahmer (Committee Member)
89 p.

Recommended Citations

Citations

  • Go, C. S. (2010). Developing Antibacterials Using Cyclic Peptide Mimics of The Protein Subunit of Bacterial RNase P [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1285043815

    APA Style (7th edition)

  • Go, Cecilia. Developing Antibacterials Using Cyclic Peptide Mimics of The Protein Subunit of Bacterial RNase P. 2010. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1285043815.

    MLA Style (8th edition)

  • Go, Cecilia. "Developing Antibacterials Using Cyclic Peptide Mimics of The Protein Subunit of Bacterial RNase P." Master's thesis, Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1285043815

    Chicago Manual of Style (17th edition)