Hydrogen Sulfide From Cysteine Desulfurase, Not 3-Mercaptopyruvate Sulfurtransferase, Contributes to Sustaining Cell Growth and Bioenergetics in E. coli Under Anaerobic Conditions

Abstract

Endogenous hydrogen sulfide (H2S), which is primarily generated by 3-mercaptopyruvate sulfurtransferase (3-MST) in Escherichia coli (E. coli) under aerobic conditions, renders bacteria highly resistant to oxidative stress. However, the biosynthetic pathway and physiological role of this gas under anaerobic conditions remains largely unknown. In the present study, we demonstrate that cysteine desulfurase (IscS), not 3-MST, is the primary source of endogenous H2S in E. coli under anaerobic conditions. A significant decrease in H2S production under anaerobic conditions was observed in E. coli upon deletion of IscS, but not in 3-MST-deficient bacteria (ΔmstA). Furthermore, the H2S-producing activity of recombinant IscS using L-cysteine as a substrate exhibited an approximately 2.6-fold increase in the presence of dithiothreitol (DTT), indicating that H2S production catalyzed by IscS was greatly increased under reducing conditions. The activity of IscS was regulated under the different redox conditions and the midpoint redox potential was determined to be −329 ± 1.6 mV. Moreover, in E. coli cells H2S production from IscS is regulated under oxidative and reductive stress. A mutant E. coli (ΔiscS) strain lacking a chromosomal copy of the IscS-encoding gene iscS showed significant growth defects and low levels of ATP under both aerobic and anaerobic conditions. The growth defects could be fully restored after addition of 500 μM Na2S (an H2S donor) under anaerobic conditions, but not by the addition of cysteine, sodium sulfite or sodium sulfate. We also showed that the addition of 500 μM Na2S to culture medium stimulates ATP synthesis in the mutant E. coli (ΔiscS) strain in the logarithmic growth phase but suppresses ATP synthesis in wild-type E. coli. Our results reveal a new H2S-producing pathway in E. coli under anaerobic conditions and show that hydrogen sulfide from IscS contributes to sustaining cell growth and bioenergetics under oxygen-deficient conditions.

The sulfur formation system mediating extracellular cysteine‐cystine recycling in Fervidobacterium islandicum AW‐1 is associated with keratin degradation

“…4B). This plausible scenario is further supported by recent results that SufS produces H 2 S via the persulfide intermediate under anaerobic conditions (Wang et al, 2019).…”

H2S and reactive sulfur signaling at the host-bacterial pathogen interface

“…2A). Bacteria generally encode either 3MST or CBS/CSE, and it was recently demonstrated that L-cysteine desulfhydrases and cysteine desulfurases also contribute to H 2 S biogenesis in Escherichia coli (39,40). In addition, two groups recently reported the discovery of a glycyl radical enzyme from Bilophila wadsworthia that catalyzes C-S bond cleavage in the catabolism of tissueabundant taurine and the analogous alcohol isethionate (2hydroxyethanesulfonate) (41,42).…”

H2O2-Mediated Oxidative Stress Enhances Cystathionine γ-Lyase-Derived H2S Synthesis via a Sulfenic Acid Intermediate

“…Generation of H 2 S by CSE was measured using L-cysteine as the substrate in a spectrophotometric assay described previously [ 13 , 14 , 15 ]. The reaction of H 2 S production by CSE with lead acetate to form lead sulfide was monitored at 390 nm.…”