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Sato Y, Yabuki T, Adachi N, Moriya T, Arakawa T, Kawasaki M, Yamada C, Senda T, Fushinobu S, Wakagi T. Crystallographic and cryogenic electron microscopic structures and enzymatic characterization of sulfur oxygenase reductase from Sulfurisphaera tokodaii. J Struct Biol X 2020; 4:100030. [PMID: 32775998 PMCID: PMC7398979 DOI: 10.1016/j.yjsbx.2020.100030] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Revised: 06/20/2020] [Accepted: 06/30/2020] [Indexed: 02/07/2023]
Abstract
Sulfur oxygenase reductase (SOR) was biochemically and structurally characterized. High resolution structures of SOR were determined by crystallography and cryo-EM. Twenty-four identical subunits of SOR form a hollow sphere. Catalytic components exhibited different features in the crystal and cryo-EM structures.
Sulfur oxygenase reductases (SORs) are present in thermophilic and mesophilic archaea and bacteria, and catalyze oxygen-dependent oxygenation and disproportionation of elemental sulfur. SOR has a hollow, spherical homo-24-mer structure and reactions take place at active sites inside the chamber. The crystal structures of SORs from Acidianus species have been reported. However, the states of the active site components (mononuclear iron and cysteines) and the entry and exit paths of the substrate and products are still in dispute. Here, we report the biochemical and structural characterizations of SORs from the thermoacidophilic archaeon Sulfurisphaera tokodaii (StSOR) and present high-resolution structures determined by X-ray crystallography and cryogenic electron microscopy (cryo-EM). The crystal structure of StSOR was determined at 1.73 Å resolution. At the catalytic center, iron is ligated to His86, His90, Glu114, and two water molecules. Three conserved cysteines in the cavity are located 9.5–13 Å from the iron and were observed as free thiol forms. A mutational analysis indicated that the iron and one of the cysteines (Cys31) were essential for both activities. The cryo-EM structure was determined at 2.24 Å resolution using an instrument operating at 200 kV. The two structures determined by different methodologies showed similar main chain traces, but the maps exhibited different features at catalytically important components. A possible role of StSOR in the sulfur metabolism of S. tokodaii (an obligate aerobe) is discussed based on this study. Given the high resolution achieved in this study, StSOR was shown to be a good benchmark sample for cryo-EM.
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Key Words
- AaSOR, Acidianus ambivalens SOR
- AqSOR, Aquifex aeolicus SOR
- Archaea
- AtSOR, Acidianus tengchongensis SOR
- CTF, contrast transfer function
- Cryogenic electron microscopy
- DTNB, 5,5′-dithiobis(2-nitrobenzoic acid)
- FSC, Fourier shell correlation
- HnSOR, Halothiobacillus neapolitanus SOR
- Nonheme mononuclear iron center
- PAGE, polyacrylamide gel electrophoresis
- RMSD, root mean square deviation
- SD, standard deviation
- SDS, sodium dodecyl sulfate
- SOR, sulfur oxygenase reductase
- SbSOR, Sulfobacillus thermosulfidooxidans SOR
- StSOR, Sulfurisphaera tokodaii SOR
- Sulfur metabolism
- TpSOR, Thioalkalivibrio paradoxus SOR
- X-ray crystallography
- cryo-EM, cryogenic electron microscopy
- pCMB, p-chloromercuribenzoate
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Affiliation(s)
- Yuta Sato
- Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Takashi Yabuki
- Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Naruhiko Adachi
- Structural Biology Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
| | - Toshio Moriya
- Structural Biology Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
| | - Takatoshi Arakawa
- Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.,Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Masato Kawasaki
- Structural Biology Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
| | - Chihaya Yamada
- Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.,Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Toshiya Senda
- Structural Biology Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
| | - Shinya Fushinobu
- Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.,Collaborative Research Institute for Innovative Microbiology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Takayoshi Wakagi
- Department of Biotechnology, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
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