Use of nfsB, encoding nitroreductase, as a reporter gene to determine the mutational spectrum of spontaneous mutations in Neisseria gonorrhoeae

A nanoengineered tandem nitroreductase: designing a robust prodrug-activating nanoreactor

Nitroreductases are important enzymes for a variety of applications, including cancer therapy and bioremediation. They often require encapsulation to improve stability and activity. We focus on genetically encoded encapsulation of nitroreductases within protein capsids, like encapsulins. Our study showcases the encapsulation of nitroreductase NfsB as functional dimers within encapsulins, which enhances protein activity and stability in diverse conditions. Mutations within the pore region are beneficial for activity of the encapsulated enzyme, potentially by increasing diffusion rates. Cryogenic electron microscopy reveals the overall architecture of the encapsulated dimeric NfsB within the nanoreactor environment and identifies multiple pore states in the shell. These findings highlight the potential of encapsulins as versatile tools for enhancing enzyme performance across various fields.

Targeting the substrate preference of a type I nitroreductase to develop antitrypanosomal quinone-based prodrugs

Nitroheterocyclic prodrugs are used to treat infections caused by Trypanosoma cruzi and Trypanosoma brucei. A key component in selectivity involves a specific activation step mediated by a protein homologous with type I nitroreductases, enzymes found predominantly in prokaryotes. Using data from determinations based on flavin cofactor, oxygen-insensitive activity, substrate range, and inhibition profiles, we demonstrate that NTRs from T. cruzi and T. brucei display many characteristics of their bacterial counterparts. Intriguingly, both enzymes preferentially use NADH and quinones as the electron donor and acceptor, respectively, suggesting that they may function as NADH:ubiquinone oxidoreductases in the parasite mitochondrion. We exploited this preference to determine the trypanocidal activity of a library of aziridinyl benzoquinones against bloodstream-form T. brucei. Biochemical screens using recombinant NTR demonstrated that several quinones were effective substrates for the parasite enzyme, having K(cat)/K(m) values 2 orders of magnitude greater than those of nifurtimox and benznidazole. In tests against T. brucei, antiparasitic activity mirrored the biochemical data, with the most potent compounds generally being preferred enzyme substrates. Trypanocidal activity was shown to be NTR dependent, as parasites with elevated levels of this enzyme were hypersensitive to the aziridinyl agent. By unraveling the biochemical characteristics exhibited by the trypanosomal NTRs, we have shown that quinone-based compounds represent a class of trypanocidal compound.