Staphylococcus aureus CstB Is a Novel Multidomain Persulfide Dioxygenase-Sulfurtransferase Involved in Hydrogen Sulfide Detoxification

Abstract

Hydrogen sulfide (H2S) is both a lethal gas and an emerging gasotransmitter in humans, suggesting that cellular H2S level must be tightly regulated. CstB is encoded by the cst operon of the major human pathogen Staphylococcus aureus (S. aureus) and is under the transcriptional control of the persulfide sensor CstR and H2S. Here we show that CstB is a multifunctional Fe(II)-containing persulfide dioxygenase (PDO), analogous to the vertebrate protein ETHE1 (Ethylmalonic Encephalopathy Protein 1). Chromosomal deletion of ethe1 is fatal in vertebrates. In the presence of molecular oxygen (O2), hETHE1 oxidizes glutathione persulfide (GSSH) to generate sulfite and reduced glutathione. In contrast, CstB oxidizes major cellular low molecular weight (LMW) persulfide substrates from S. aureus, coenzyme A persulfide (CoASSH) and bacillithiol persulfide (BSSH), directly to generate thiosulfate (TS) and reduced thiols, thereby avoiding the cellular toxicity of sulfite. Both Cys201 in the N-terminal PDO domain (CstBPDO) and Cys408 in the C-terminal rhodanese domain (CstBRhod) strongly enhance the TS generating activity of CstB. CstB also possesses persulfide transferase (PT; reverse rhodanese) activity which generates TS when provided with LMW persulfides and sulfite, as well as conventional thiosulfate transferase (TST; rhodanese) activity; both activities require Cys408. CstB protects S. aureus against H2S toxicity with C201S and C408S cstB genes unable to rescue a NaHS-induced ΔcstB growth phenotype. Induction of the cst operon by NaHS reveals that functional CstB impacts the cellular TS concentrations. These data collectively suggest that CstB may have evolved to facilitate the clearance of LMW persulfides that occur upon the elevation of the level of cellular H2S and hence may have an impact on bacterial viability under H2S stress, in concert with the other enzymes encoded by the cst operon.

Thiosulfate sulfurtransferase-like domain–containing 1 protein interacts with thioredoxin

“…This product inhibition behavior of TSTD1 is similar to that of the PRF protein, which has a single rhodanese sulfurtransferase domain fused to a persulfide dioxygenase (24). In contrast, the Staphylococcus aureus CstB, which has a persulfide dioxygenase fused to a tandem repeat of rhodanese domains, catalyzes sulfur transfer from coenzyme A persulfide or bacillithiol persulfide to sulfite as an acceptor (23).…”

“…Alternatively, the rhodanese domain can be present in a tandem repeat, as in rhodanese and MST, where the active sites are located in a cleft between the N-and C-terminal domains (14,15). Finally, rhodanese domains are fused to other protein domains as in Cdc25 phosphatase (20) or in the PRF and CstB proteins (23,24).…”

“…Alternatively, the rhodanese domain can be present in a tandem repeat, as in rhodanese and MST, where the active sites are located in a cleft between the N-and C-terminal domains (14,15). Finally, rhodanese domains are fused to other protein domains as in Cdc25 phosphatase (20) or in the PRF and CstB proteins (23,24).Sulfurtransferases are ubiquitously distributed enzymes that function in a range of pathways including sulfur metabolism, iron-sulfur cluster formation, selenium metabolism, and cyanide detoxification (13,14,(25)(26)(27)(28). In humans, there are five sulfurtransferases including mitochondrial rhodanese and MST, which is found in the cytoplasmic and mitochondrial compartments (29,30).…”

Sulfide-responsive transcriptional repressor SqrR functions as a master regulator of sulfide-dependent photosynthesis

“…These studies establish that the sulfide-regulated repressor SqrR allows R. capsulatus to adapt to changes in sulfide availability via thiol persulfidation chemistry on SqrR, which we hypothesize involves the intermediacy of RSS in cells. The functional characteristics of SqrR appear largely analogous to those of CstR in S. aureus (26), which also regulates an H 2 S oxidation and detoxification system (46), despite vastly distinct structural scaffolds (47). Further elucidation of the functional role(s) of persulfide trafficking and sulfide homeostasis in R. capsulatus promises a better understanding of how these processes impact photosynthesis in this industrially important bacterium.…”

Polymorphic Variants of Human Rhodanese Exhibit Differences in Thermal Stability and Sulfur Transfer Kinetics

“…Furthermore, interaction between the persulfide dioxygenase and rhodanese could increase the effective concentration of sulfite, allowing this reactive intermediate to channel between the two active sites. Natural fusions of rhodanese and persulfide dioxygenase are found in bacteria, suggesting that a functional interaction between them might exist in other organisms (13,35,37). …”