Thiosulfate dehydrogenases are bacterial cytochromes that contribute to the oxidation of inorganic sulfur. The active sites of these enzymes contain low-spin -type heme with Cys/His axial ligation. However, the reduction potentials of these hemes are several hundred mV more negative than that of the thiosulfate/tetrathionate couple (, +198 mV), making it difficult to rationalize the thiosulfate oxidizing capability. Here, we describe the reaction of thiosulfate dehydrogenase (TsdA) with sulfite, an analogue of thiosulfate. The reaction leads to stoichiometric conversion of the active site Cys to cysteinyl sulfonate (C-CH-S-SO) such that the protein exists in a form closely resembling a proposed intermediate in the pathway for thiosulfate oxidation that carries a cysteinyl thiosulfate (C-CH-S-SSO). The active site heme in the stable sulfonated protein displays an approximately 200 mV more positive than the Cys/His-ligated state. This can explain the thiosulfate oxidizing activity of the enzyme and allows us to propose a catalytic mechanism for thiosulfate oxidation. Substrate-driven release of the Cys heme ligand allows that side chain to provide the site of substrate binding and redox transformation; the neighboring heme then simply provides a site for electron relay to an appropriate partner. This chemistry is distinct from that displayed by the Cys-ligated hemes found in gas-sensing hemoproteins and in enzymes such as the cytochromes P450. Thus, a further class of thiolate-ligated hemes is proposed, as exemplified by the TsdA centers that have evolved to catalyze the controlled redox transformations of inorganic oxo anions of sulfur.
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http://dx.doi.org/10.1021/jacs.2c06062 | DOI Listing |
Nanomaterials (Basel)
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Center for Genomics and Precision Medicine, Institute of Bioscience and Technology, Texas A&M Health Science Center, Houston, TX 77030, USA.
Harsh acid oxidation of activated charcoal transforms an insoluble carbon-rich source into water-soluble, disc structures of graphene decorated with multiple oxygen-containing functionalities. We term these pleiotropic nano-enzymes as "pleozymes". A broad redox potential spans many crucial redox reactions including the oxidation of hydrogen sulfide (HS) to polysulfides and thiosulfate, dismutation of the superoxide radical (O*), and oxidation of NADH to NAD.
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Anesthesia Center for Critical Care Research, Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA. Electronic address:
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View Article and Find Full Text PDFISME Commun
January 2024
Department of Geosciences, Princeton University, Princeton, NJ 08540, United States.
Long-isolated subsurface brine environments (Ma-Ga residence times) may be habitable if they sustainably provide substrates, e.g. through water-rock reactions, that support microbial catabolic energy yields exceeding maintenance costs.
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December 2024
Department of Biotechnology, College of Science, Taif University, Taif, Saudi Arabia.
Thin films of PbS, both undoped and cobalt-doped (Co-PbS), were produced on glass substrates using the straightforward and controllable approach of sequential ionic layer adsorption and reaction (SILAR). The reactive substances employed to deposit the PbS thin films were lead nitrate (Pb(NO)), cobalt nitrate (Co(NO₃)₂(H₂O)₆), sodium thiosulphate (NaSO) and HO for different dipping concentrations of lead and cobalt. The films were adherent to the substrate and were compact, and crack-free with a shiny silver color.
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Laboratory of Arctic Mineralogy and Material Sciences, Kola Science Centre, Russian Academy of Sciences, Apatity 184209, Russian Federation.
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