Abstract
Sulfane sulfur species including hydrogen polysulfide and organic persulfide are newly recognized normal cellular components, and they participate in signaling and protect cells from oxidative stress. Their production has been extensively studied, but their removal is less characterized. Herein, we showed that sulfane sulfur at high levels was toxic to Escherichia coli under both anaerobic and aerobic conditions. OxyR, a well-known regulator against H2O2, also sensed sulfane sulfur, as revealed via mutational analysis, constructed gene circuits, and in vitro gene expression. Hydrogen polysulfide modified OxyR at Cys199 to form a persulfide OxyR C199-SSH, and the modified OxyR activated the expression of thioredoxin 2 and glutaredoxin 1. The two enzymes are known to reduce sulfane sulfur to hydrogen sulfide. Bioinformatics analysis indicated that OxyR homologs are widely present in bacteria, including obligate anaerobic bacteria. Thus, the OxyR sensing of sulfane sulfur may represent a preserved mechanism for bacteria to deal with sulfane sulfur stress.
Highlights
H2S has been proposed as a gasotransmitter because it is involved in many physiological and pathological processes in animals and plants, such as ageing (Hine et al, 2015), neuromodulation (Abe & Kimura, 1996), cancer cell proliferation (Cai et al, 2010), metabolic reprogramming (Gao et al, 2015), and stomatal closure in plant (Lisjak et al, 2010)
We cultured early-log phased E. coli cells in Lysogeny broth (LB) medium and used the sulfane sulfur sensitive probe SSP4 (Fig. 1A) to detect intracellular sulfane sulfur
In this study, we reported the fifth type modification of OxyR, C199-SSH, which is modified by H2Sn
Summary
H2S has been proposed as a gasotransmitter because it is involved in many physiological and pathological processes in animals and plants, such as ageing (Hine et al, 2015), neuromodulation (Abe & Kimura, 1996), cancer cell proliferation (Cai et al, 2010), metabolic reprogramming (Gao et al, 2015), and stomatal closure in plant (Lisjak et al, 2010). Reactive sulfane sulfur species include hydrogen polysulfides (H2Sn, n≥2), organic polysulfides (RSSnH, RSSnR, n≥2), and organic persulfides (RSSH), which can be produced directly from cysteine or cystine, and they are considered as normal components in both prokaryotic and eukaryotic cells (Sawa et al, 2018; Yadav et al, 2016). They possess both nucleophilic and electrophilic characteristics, while thiols (cysteine, GSH, etc.) are generally nucleophilic (Ono et al, 2014; Park et al, 2015). Intracellular sulfane sulfur is likely maintained within a range for microorganisms under normal conditions
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