Regulation of quinone detoxification by the thiol stress sensing DUF24/MarR‐like repressor, YodB in Bacillus subtilis

Abstract

SummaryRecently, we showed that the MarR-type repressor YkvE (MhqR) regulates multiple dioxygenases/ glyoxalases, oxidoreductases and the azoreductase encoding yvaB (azoR2) gene in response to thiolspecific stress conditions, such as diamide, catechol and 2-methylhydroquinone (MHQ). Here we report on the regulation of the yocJ (azoR1) gene encoding another azoreductase by the novel DUF24/MarR-type repressor, YodB after exposure to thiol-reactive compounds. DNA binding activity of YodB is directly inhibited by thiol-reactive compounds in vitro. Mass spectrometry identified YodB-Cys-S-adducts that are formed upon exposure of YodB to MHQ and catechol in vitro. This confirms that catechol and MHQ are auto-oxidized to toxic ortho-and para-benzoquinones which act like diamide as thiol-reactive electrophiles. Mutational analyses further showed that the conserved Cys6 residue of YodB is required for optimal repression in vivo and in vitro while substitution of all three Cys residues of YodB affects induction of azoR1 transcription. Finally, phenotype analyses revealed that both azoreductases, AzoR1 and AzoR2 confer resistance to catechol, MHQ, 1,4-benzoquinone and diamide. Thus, both azoreductases that are controlled by different regulatory mechanisms have common functions in quinone and azo-compound reduction to protect cells against the thiol reactivity of electrophiles.

Molecular mechanism of quinone signaling mediated through S-quinonization of a YodB family repressor QsrR

“…Human pathogens such as S. aureus, on the other hand, must develop a certain counteractive defense mechanism to tackle quinone molecules. To study quinone signaling, we focused on S. aureus QsrR (SAV2123), a homolog of B. subtilis quinone stress- sensing regulator YodB (38% identities, 61% positives) (19,21). We first performed a disk-diffusion assay to examine the role of QsrR in response to quinone stress.…”

“…In Escherichia coli, the anoxic redox control ArcAB is considered a quinone-sensing two-component system (17,18). In Bacillus subtilis, the thiol-stress sensing regulator YodB is a prototypical transcriptional regulator responsible for quinone sensing and detoxification (19)(20)(21).…”

Regulation of Quinone Oxidoreductase by the Redox-sensing Transcriptional Regulator QorR in Corynebacterium glutamicum

“…S1B). Cys-6 of YodB has been shown to play a role in DNA binding and response to thiol-reactive compounds (2). Thus, the cysteine residue of the N-terminal region of the DUF24 family proteins is likely to play a regulatory role.…”

“…Although HxlR is necessary for formaldehyde-induced expression of the operon, the finer details as to how formaldehyde modulates hxlAB expression are still not clear. YodB negatively controls expression of spx, azoR1, and yodC, genes involved in oxidative stress response (2,3). The DNAbinding activity of YodB is inhibited by thiol-reactive compounds, and its cysteine residues function in redox sensing (2).…”

“…Real-time qRT-PCR-A one-step real-time quantitative reverse transcription-PCR (qRT-PCR) 2 was performed with the Power SYBR Green PCR Master Mix (Applied BioSystems) and a pair of gene-specific primers (supplemental Table S1) by using the 7500 Fast Real-time PCR system (Applied BioSystems) as described previously (18). Relative ratios were normalized with the value for 16 S rRNA.…”