Characterization of membrane-bound sulfane reductase: A missing link in the evolution of modern day respiratory complexes

• Published in: The Journal of biological chemistry 2018-10, Vol.293 (43), p.16687-16696
• Main Authors: Wu, Chang-Hao, Schut, Gerrit J., Poole, Farris L., Haja, Dominik K., Adams, Michael W.W.
• Format: Article
• Language: English
• Subjects: Archaea; archaea hydrogenase; Archaeal Proteins - genetics; Archaeal Proteins - metabolism; BASIC BIOLOGICAL SCIENCES; Biochemistry & Molecular Biology; Bioenergetics; Catalytic Domain; Cell Membrane - metabolism; Complex; Complex I; Electron Transport Complex I - genetics; Electron Transport Complex I - metabolism; evolution; hydrogen sulfide; hydrogenase; membrane energetics; membrane enzyme; Membrane Proteins - genetics; Membrane Proteins - metabolism; Oxidation-Reduction; oxidation-reduction (redox); Oxidoreductases - genetics; Oxidoreductases - metabolism; protein purification; Pyrococcus furiosus - enzymology; Pyrococcus furiosus - growth & development; respiration; respiratory complex; Sulfides - chemistry; sulfur
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.RA118.005092

Hyperthermophilic archaea contain a hydrogen gas–evolving,respiratory membrane–bound NiFe-hydrogenase (MBH) that is very closely related to the aerobic respiratory complex I. During growth on elemental sulfur (S°), these microorganisms also produce a homologous membrane-bound complex (MBX), which generates H2S. MBX evolutionarily links MBH to complex I, but its catalytic function is unknown. Herein, we show that MBX reduces the sulfane sulfur of polysulfides by using ferredoxin (Fd) as the electron donor, and we rename it membrane-bound sulfane reductase (MBS). Two forms of affinity-tagged MBS were purified from genetically engineered Pyrococcus furiosus (a hyperthermophilic archaea species): the 13-subunit holoenzyme (S-MBS) and a cytoplasmic 4-subunit catalytic subcomplex (C-MBS). S-MBS and C-MBS reduced dimethyl trisulfide (DMTS) with comparable Km (∼490 μm) and Vmax values (12 μmol/min/mg). The MBS catalytic subunit (MbsL), but not that of complex I (NuoD), retains two of four NiFe-coordinating cysteine residues of MBH. However, these cysteine residues were not involved in MBS catalysis because a mutant P. furiosus strain (MbsLC85A/C385A) grew normally with S°. The products of the DMTS reduction and properties of polysulfides indicated that in the physiological reaction, MBS uses Fd (Eo′ = −480 mV) to reduce sulfane sulfur (Eo′ −260 mV) and cleave organic (RSnR, n ≥ 3) and anionic polysulfides (Sn2−, n ≥ 4) but that it does not produce H2S. Based on homology to MBH, MBS also creates an ion gradient for ATP synthesis. This work establishes the electrochemical reaction catalyzed by MBS that is intermediate in the evolution from proton- to quinone-reducing respiratory complexes.