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Characterization of Catalytic Metallodrugs: Advances towards Novel Antibiotics

Alexander, Jessica L
http://rave.ohiolink.edu/etdc/view?acc_num=osu1503313186810767

Abstract Details

2017, Doctor of Philosophy, Ohio State University, Chemistry.
Antimicrobial peptides are short, amphipathic peptides that are produced by the innate immune system in order to protect hosts from pathogens. They have been shown to have broad-range range antimicrobial activity towards microorganisms and exert their activity through a variety of mechanisms that include inhibiting DNA and RNA replication, inhibiting protein synthesis, permeabilizing the cell membrane, disrupting proton and ion transmembrane gradients, and inhibiting cell wall biosynthesis. We have investigated the influence of the amino terminal copper and nickel binding (ATCUN) motif on the mode of action for several AMPs including derivatives of indolicidin, CP10A, Sub5, ovispirin-3 (OV-3), and Bac2A. Cu-ATCUN derivatives of indolicidin and CP10A were shown to target cells by DNA nicking, similar to the mode of action of indolicidin and CP10A, as well as induce lipid oxidation without permeabilizing the membrane. The Cu-ATCUN derivatives of indolicidin showed enhanced activity towards A. baumannii and S. pneumoniae, possibly due to targeting both the membrane bilayer and inducing oxidative damage as well as nicking of genomic DNA. The Cu-ATCUN OV-3 derivatives demonstrated increased antimicrobial activity towards a broad range of bacteria, relative to OV-3, with MICs as low as 1.3 ± 0.6 µM. Each of the peptides was able to bind DNA and RNA with micromolar affinity, but did not display nuclease activity in vivo. The ATCUN OV-3 derivatives also displayed increased membrane leakage and lipid peroxidation relative to Cu-GGH and OV-3 alone. These data suggest that the Cu-ATCUN derivatives inhibit bacteria by binding to the membrane, promoting oxidative damage of the lipids which then disrupts the bilayer, resulting in cell death. This stands in contrast to the mode of action of OV-3 alone, which permeabilizes the membrane without lipid oxidation. Cu-ATCUN derivatives of Sub5 without an N-terminal GGC sequence show increased antimicrobial activity for a variety of microbes relative to Sub5 with MICs as low as 0.3 ± 0.1 µM towards E. faecium. Although all of the Sub5 derivatives are able to bind nucleic acids in vitro, only the Cu-ATCUN derivatives without an N-terminal GGC sequence and Sub5 also display nuclease activity in vivo towards the bacterial genome. These ATCUN Sub5 derivatives also showed high levels of lipid oxidation and were able to bind and penetrate the lipid bilayer. All of the Sub5 derivatives had nuclease activity in S. epidermidis and the Cu-ATCUN derivatives showed lower levels of lipid oxidation compared to E. coli. Despite inducing oxidative damage to the membrane bilayer in S. epidermidis, the Cu-ATCUN derivatives did not have improved activity over Sub5. OV-3 and Bac2A derivatives demonstrated broad-spectrum nuclease activity towards DNA and several RNAs. The peptides showed Michaelis-Menten kinetics towards pUC19 DNA, 16s A-site rRNA, HCV SLIV, and HCV SLIIb with the exception of the Cu-ATCUN derivative of Bac2A towards SLIIb. This work demonstrates that Cu-ATCUN derivatives of antimicrobial peptides are able to target a variety of molecules and inhibit bacteria through irreversible oxidative damage of their targets. Importantly, they are able to inhibit microorganisms with enhanced activity and by distinct modes of action relative to their parental peptides, and, thus, are a promising approach to develop novel antibiotics.
James Cowan (Advisor)
Ross Dalbey (Committee Member)
Claudia Turro (Committee Member)
Stuart Cooper (Committee Member)
222 p.
Biochemistry; Chemistry; Inorganic Chemistry

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Citations

  • Alexander, J. L. (2017). Characterization of Catalytic Metallodrugs: Advances towards Novel Antibiotics [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1503313186810767

    APA Style (7th edition)

  • Alexander, Jessica. Characterization of Catalytic Metallodrugs: Advances towards Novel Antibiotics. 2017. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1503313186810767.

    MLA Style (8th edition)

  • Alexander, Jessica. "Characterization of Catalytic Metallodrugs: Advances towards Novel Antibiotics." Doctoral dissertation, Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1503313186810767

    Chicago Manual of Style (17th edition)

osu1503313186810767
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This open access ETD is published by The Ohio State University and OhioLINK.