Does the Transcription Factor NemR Use a Regulatory Sulfenamide Bond to Sense Bleach?

Abstract

Reactive chlorine species (RCS), such as hypochlorous acid (i.e., bleach), are antimicrobial oxidants produced by the innate immune system. Like many redox-regulated transcription factors, the Escherichia coli repressor NemR responds to RCS by using the reversible oxidation of highly conserved cysteines to alter its DNAbinding affinity. However, earlier work showed that RCS response in NemR does not depend on any commonly known oxidative cysteine modifications. We have now determined the crystal structure of NemR, showing that the regulatory cysteine, Cys106, is in close proximity to a highly conserved lysine (Lys175). We used crystallographic, biochemical, and mass spectrometric analyses to analyze the role of this lysine residue in RCS sensing. Based on our results, we hypothesize that RCS treatment of NemR results in the formation of a reversible Cys106-Lys175 sulfenamide bond. This is, to our knowledge, the first description of a protein whose function is regulated by a cysteine-lysine sulfenamide thiol switch, constituting a novel addition to the biological repertoire of functional redox switches. Antioxid. Redox Signal. 23, 747-754.

Adaptation to the coupling of glycolysis to toxic methylglyoxal production in tpiA deletion strains of Escherichia coli requires synchronized and counterintuitive genetic changes

“…5 Mutations that affect the transcription factor NemR that allowed for expression of the gloA detox pathway (Ozyamak et al, 2013). A) Crystal structure of the nemR multimer (Gray et al, 2015). A mutation that alters NemR binding to the regulatory region are annotated in red.…”

Response ofPseudomonas aeruginosato the innate immune system-derived oxidants hypochlorous acid and hypothiocyanous acid

“…These include the Bacillus subtilis transcriptional factors OhrR, HypR and PerR and the E. coli transcriptional factors NemR, HypT and RclR (10)(11)(12)(13)(14). All of the HOCl-sensing transcriptional regulators, apart from HypT, respond to HOCl through oxidation of cysteines, resulting in disulphide bond formation and activation or derepression of the regulators' target genes (10)(11)(12)(14)(15)(16). Instead, HypT responds to HOCl through oxidation of its methionine residues (17).…”

Two distinct mechanisms of transcriptional regulation by the redox sensor YodB

“…Among the thiol-based oxidation regulators, Escherichia coli OxyR (5,6), Xanthomonas campestris OhrR (7,8), Bacillus subtilis OhrR (9), Pseudomonas aeruginosa MexR (10), and E. coli NemR (11,12) are representatives that demonstrate how well these regulators sense organic peroxide by forming disulfide bonds between two distantly located cysteines (10). OxyR oxidation leads to the formation of intramolecular disulfide bonds and alters the interaction between the OxyR tetramer and the DNA sites upstream from the OxyR-regulated genes, which enhances OxyR DNA recognition capability (5,6).…”

“…As with X. campestris OhrR, MexR forms intermolecular disulfide bonds in response to oxidative stress, which results in a rigid body rotation of the DNA-recognition helices, attenuating DNA-binding affinity (10). E. coli NemR possesses a redox switch that senses either electrophiles or reactive chlorine species by the formation of disulfide bonds (11) or a reversible sulfenamide bond (12), respectively. The representative redox regulators E. coli OxyR, X. campestris OhrR, B. subtilis OhrR, P. aeruginosa MexR, and E. coli NemR demonstrate how these proteins are structurally influenced by the formation of disulfide bonds that are induced by oxidative stress.…”