skip to main content


This content will become publicly available on September 26, 2024

Title: Stabilizing Pseudouridimycin: Synthesis, RNA Polymerase Inhibitory Activity, and Antibacterial Activity of Dipeptide‐Modified Analogues
Abstract

Pseudouridimycin (PUM) is a microbially produced C‐nucleoside dipeptide that selectively targets the nucleotide addition site of bacterial RNA polymerase (RNAP) and that has a lower rate of spontaneous resistance emergence relative to current drugs that target RNAP. Despite its promising biological profile, PUM undergoes relatively rapid decomposition in buffered aqueous solutions. Here, we describe the synthesis, RNAP‐inhibitory activity, and antibacterial activity of chemically stabilized analogues of PUM. These analogues feature targeted modifications that mitigate guanidine‐mediated hydroxamate bond scission. A subset of analogues in which the central hydroxamate is replaced with amide or hydrazide isosteres retain the antibacterial activity of the natural product.

 
more » « less
Award ID(s):
2109008
NSF-PAR ID:
10484941
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
ChemMedChem
Volume:
19
Issue:
1
ISSN:
1860-7179
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract

    Previously, a boronium salt possessing a terminal benzyl group was reported to have greater antibacterial activity than a commercial quaternary ammonium disinfectant solution againstEscherichia coli,Pseudomonas aeruginosa, andStaphylococcus aureus. Results of the current study indicate that the same boronium salt without a benzyl group, exhibited equal or better antifungal activity against actively growingCandida albicansyeast andAspergillus fumigatusmold when compared to the same quat disinfectant. This same compound also displayed antifungal activity against dormantA. fumigatusspores comparable to the quat disinfectant. In contrast, the boronium ion with a benzyl group was 4–16X less effective than either the non‐benzylated form or quat disinfectant for all 3 fungal test conditions. The observation that the boronium salt without a benzyl group exhibited substantial antifungal activity in the current study but did not display any antibacterial activity in the previous study is of particular interest. This finding represents a flip‐flop outcome from the previous bacterial testing. It suggests that the presence of a terminal benzyl group greatly influences the boronium ion's ability to interact with fungal membranes.

     
    more » « less
  2. Abstract

    We investigated the ability of four plant and soil‐associated fungi to modify or degrade siderophore structures leading to reduced siderophore iron‐affinity in iron‐limited and iron‐replete cultures.Pyrenophora biseptata, a melanized fungus from wheat roots, was effective in inactivating siderophore iron‐chelating moieties. In the supernatant solution, the tris‐hydroxamate siderophore desferrioxamine B (DFOB) underwent a stepwise reduction of the three hydroxamate groups in DFOB to amides leading to a progressive loss in iron affinity. A mechanism is suggested based on the formation of transient ferrous iron followed by reduction of the siderophore hydroxamate groups during fungal high‐affinity reductive iron uptake.P. biseptataalso produced its own tris‐hydroxamate siderophores (neocoprogen I and II, coprogen and dimerum acid) in iron‐limited media and we observed loss of hydroxamate chelating groups during incubation in a manner analogous to DFOB. A redox‐based reaction was also involved with the tris‐catecholate siderophore protochelin in which oxidation of the catechol groups to quinones was observed. The new siderophore inactivating activity of the wheat symbiontP. biseptatais potentially widespread among fungi with implications for the availability of iron to plants and the surrounding microbiome in siderophore‐rich environments.

     
    more » « less
  3. Abstract

    Each year, thousands of patients die from antimicrobial‐resistant bacterial infections that fail to respond to conventional antibiotic treatment. Antimicrobial polymers are a promising new method of combating antibiotic‐resistant bacterial infections. We have previously reported the synthesis of a series of narrow‐spectrum peptidomimetic antimicrobial polyurethanes that are effective against Gram‐negative bacteria, such asEscherichia coli; however, these polymers are not effective against Gram‐positive bacteria, such asStaphylococcus aureus. With the aim of understanding the correlation between chemical structure and antibacterial activity, we have subsequently developed three structural variants of these antimicrobial polyurethanes using post‐polymerization modification with decanoic acid and oleic acid. Our results show that such modifications converted the narrow‐spectrum antibacterial activity of these polymers into broad‐spectrum activity against Gram‐positive species such asS. aureus, however, also increasing their toxicity to mammalian cells. Mechanistic studies of bacterial membrane disruption illustrate the differences in antibacterial action between the various polymers. The results demonstrate the challenge of balancing antimicrobial activity and mammalian cell compatibility in the design of antimicrobial polymer compositions. © 2019 Society of Chemical Industry

     
    more » « less
  4. We report the synthesis of cationic dendrons (1 st and 2 nd generations) with pendant alkyl chains of varying lengths (C 8 , C 12 , C 14 ), which are classified as cationic molecular umbrellas. In each case, the dendron surface moieties were functionalized with guanidine groups, which are fully protonated in aqueous media of pH 7.4, lending cationic character to the solute. We found that these compounds are potent membrane-disrupting antibacterial agents with dose-dependent hemolytic activities. Confocal microscopy confirmed the permeabilization of E. coli and S. aureus cell membranes. A pyrene emission assay confirms that the dendrons are unimolecularly solvated at the concentrations relevant to their antibacterial activity, although they do aggregate at higher concentrations in aqueous buffer. Most importantly, when we compare the activity of these guanidinium-functionalized umbrellas to our previously published data on ammonium-functionalized analogues, we found no significant benefits to guanidinium relative to the ammoniums. The antibacterial activities are similar in all cases tested, and the highest selectivity index was found in the ammonium series, which stands in contrast to many other classes of antibacterial agents for which guanidinylation is typically associated with enhanced activity and selectivity. 
    more » « less
  5. Abstract

    Transcription is the critical first step in expressing a gene, during which an RNA polymerase (RNAP) synthesizes an RNA copy of one strand of the DNA that encodes a gene. Here we describe a laboratory experiment that uses a single assay to probe two important steps in transcription: (1) RNAP binding to DNA, and (2) the transcriptional activity of the polymerase. Students probe both these steps in a single experiment using a fluorescence‐based electrophoretic mobility shift assay (EMSA) and commercially availableEscherichia coliRNAP. As an inquiry‐driven component, students add the transcriptional inhibitor rifampicin to reactions and draw conclusions about its mechanism of inhibition by determining whether it blocks polymerase binding to DNA or transcriptional activity. Depending on the curriculum and learning goals of individual courses, this experimental module could be easily expanded to include additional experimentation that mimics a research environment more closely. After completing the experiment students understand basic principles of transcription, mechanisms of inhibition, and the use of EMSAs to probe protein/DNA interactions.

     
    more » « less