1
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Fernandes-Martins MC, Springer C, Colman DR, Boyd ES. Acquisition of elemental sulfur by sulfur-oxidising Sulfolobales. Environ Microbiol 2024; 26:e16691. [PMID: 39206712 DOI: 10.1111/1462-2920.16691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2024] [Accepted: 08/06/2024] [Indexed: 09/04/2024]
Abstract
Elemental sulfur (S8 0)-oxidising Sulfolobales (Archaea) dominate high-temperature acidic hot springs (>80°C, pH <4). However, genomic analyses of S8 0-oxidising members of the Sulfolobales reveal a patchy distribution of genes encoding sulfur oxygenase reductase (SOR), an S8 0 disproportionating enzyme attributed to S8 0 oxidation. Here, we report the S8 0-dependent growth of two Sulfolobales strains previously isolated from acidic hot springs in Yellowstone National Park, one of which associated with bulk S8 0 during growth and one that did not. The genomes of each strain encoded different sulfur metabolism enzymes, with only one encoding SOR. Dialysis membrane experiments showed that direct contact is not required for S8 0 oxidation in the SOR-encoding strain. This is attributed to the generation of hydrogen sulfide (H2S) from S8 0 disproportionation that can diffuse out of the cell to solubilise bulk S8 0 to form soluble polysulfides (Sx 2-) and/or S8 0 nanoparticles that readily diffuse across dialysis membranes. The Sulfolobales strain lacking SOR required direct contact to oxidise S8 0, which could be overcome by the addition of H2S. High concentrations of S8 0 inhibited the growth of both strains. These results implicate alternative strategies to acquire and metabolise sulfur in Sulfolobales and have implications for their distribution and ecology in their hot spring habitats.
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Affiliation(s)
| | - Carli Springer
- Department of Microbiology and Cell Biology, Montana State University, Bozeman, Montana, USA
| | - Daniel R Colman
- Department of Microbiology and Cell Biology, Montana State University, Bozeman, Montana, USA
| | - Eric S Boyd
- Department of Microbiology and Cell Biology, Montana State University, Bozeman, Montana, USA
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2
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Edholm F, Nandy A, Reinhardt CR, Kastner DW, Kulik HJ. Protein3D: Enabling analysis and extraction of metal-containing sites from the Protein Data Bank with molSimplify. J Comput Chem 2024; 45:352-361. [PMID: 37873926 DOI: 10.1002/jcc.27242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 09/27/2023] [Accepted: 10/03/2023] [Indexed: 10/25/2023]
Abstract
Metalloenzymes catalyze a wide range of chemical transformations, with the active site residues playing a key role in modulating chemical reactivity and selectivity. Unlike smaller synthetic catalysts, a metalloenzyme active site is embedded in a larger protein, which makes interrogation of electronic properties and geometric features with quantum mechanical calculations challenging. Here we implement the ability to fetch crystallographic structures from the Protein Data Bank and analyze the metal binding sites in the program molSimplify. We show the usefulness of the newly created protein3D class to extract the local environment around non-heme iron enzymes containing a two histidine motif and prepare 372 structures for quantum mechanical calculations. Our implementation of protein3D serves to expand the range of systems molSimplify can be used to analyze and will enable high-throughput study of metal-containing active sites in proteins.
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Affiliation(s)
- Freya Edholm
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Aditya Nandy
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Clorice R Reinhardt
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - David W Kastner
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Heather J Kulik
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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3
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Kanao T. Tetrathionate hydrolase from the acidophilic microorganisms. Front Microbiol 2024; 15:1338669. [PMID: 38348185 PMCID: PMC10859504 DOI: 10.3389/fmicb.2024.1338669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Accepted: 01/15/2024] [Indexed: 02/15/2024] Open
Abstract
Tetrathionate hydrolase (TTH) is a unique enzyme found in acidophilic sulfur-oxidizing microorganisms, such as bacteria and archaea. This enzyme catalyzes the hydrolysis of tetrathionate to thiosulfate, elemental sulfur, and sulfate. It is also involved in dissimilatory sulfur oxidation metabolism, the S4-intermediate pathway. TTHs have been purified and characterized from acidophilic autotrophic sulfur-oxidizing microorganisms. All purified TTHs show an optimum pH in the acidic range, suggesting that they are localized in the periplasmic space or outer membrane. In particular, the gene encoding TTH from Acidithiobacillus ferrooxidans (Af-tth) was identified and recombinantly expressed in Escherichia coli cells. TTH activity could be recovered from the recombinant inclusion bodies by acid refolding treatment for crystallization. The mechanism of tetrathionate hydrolysis was then elucidated by X-ray crystal structure analysis. Af-tth is highly expressed in tetrathionate-grown cells but not in iron-grown cells. These unique structural properties, reaction mechanisms, gene expression, and regulatory mechanisms are discussed in this review.
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Affiliation(s)
- Tadayoshi Kanao
- Department of Agricultural and Biological Chemistry, Graduate School of Environment, Life, Natural Science, and Technology, Okayama University, Okayama, Japan
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4
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Lee EJ, Gladkov N, Miller JE, Yeates TO. Design of Ligand-Operable Protein-Cages That Open Upon Specific Protein Binding. ACS Synth Biol 2024; 13:157-167. [PMID: 38133598 DOI: 10.1021/acssynbio.3c00383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
Protein nanocages have diverse applications in medicine and biotechnology, including molecular delivery. However, although numerous studies have demonstrated the ability of protein nanocages to encapsulate various molecular species, limited methods are available for subsequently opening a nanocage for cargo release under specific conditions. A modular platform with a specific protein-target-based mechanism of nanocage opening is notably lacking. To address this important technology gap, we present a new class of designed protein cages, the Ligand-Operable Cage (LOC). LOCs primarily comprise a protein nanocage core and a fused surface binding adaptor. The geometry of the LOC is designed so that binding of a target protein ligand (or multiple copies thereof) to the surface binder is sterically incompatible with retention of the assembled state of the cage. Therefore, the tight binding of a target ligand drives cage disassembly by mass action, subsequently exposing the encapsulated cargo. LOCs are modular; direct substitution of the surface binder sequence can reprogram the nanocage to open in response to any target protein ligand of interest. We demonstrate these design principles using both a natural and a designed protein cage as the core, with different proteins acting as the triggering ligand and with different reporter readouts─fluorescence unquenching and luminescence─for cage disassembly. These developments advance the critical problem of targeted molecular delivery and detection.
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Affiliation(s)
- Eric J Lee
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095, United States
| | - Nika Gladkov
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095, United States
| | - Justin E Miller
- Molecular Biology Institute, UCLA, Los Angeles, California 90095, United States
| | - Todd O Yeates
- Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095, United States
- Molecular Biology Institute, UCLA, Los Angeles, California 90095, United States
- UCLA-DOE Institute for Genomics and Proteomics, UCLA, Los Angeles, California 90095, United States
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5
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Cryo-electron structures of the extreme thermostable enzymes Sulfur Oxygenase Reductase and Lumazine Synthase. PLoS One 2022; 17:e0275487. [PMID: 36191023 PMCID: PMC9529111 DOI: 10.1371/journal.pone.0275487] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2022] [Accepted: 09/18/2022] [Indexed: 11/05/2022] Open
Abstract
Thermostable enzymes have the potential for use in a wide variety of biotechnological applications. Cryo-electron microscopy (cryo-EM) enables the imaging of biomolecules in their native aqueous environment. Here, we present high resolution cryo-EM structures of two thermostable enzymes that exhibit multimeric cage-like structures arranged into two different point-group symmetries. First, we determined the structure of the Sulfur Oxygenase Reductase (SOR) enzyme that catalyzes both the oxygenation and disproportionation of elemental sulfur in Archea and is composed of 24 homomeric units each of MW ≃ 35 kDa arranged in octahedral symmetry. The structure of SOR from Acidianus ambivalens (7X9W) was determined at 2.78 Å resolution. The active site of each subunit inside the central nanocompartment is composed of Fe3+ coordinated to two water molecules and the three amino acids (H86, H90 and E114). Second, we determined the structure of Lumazine Synthase (LS) from Aquifex aeolicus (7X7M) at 2.33 Å resolution. LS forms a cage-like structure consisting of 60 identical subunits each of MW ≃ 15 kDa arranged in a strict icosahedral symmetry. The LS subunits are interconnected by ion-pair network. Due to their thermostability and relatively easy purification scheme, both SOR and LS can serve as a model for the catalytic and structural characterization of biocatalysts as well as a benchmark for cryo-EM sample preparation, optimization of the acquisition parameters and 3D reconstruction.
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6
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Pal N, Sinha S, Shivani, Chakraborty M. A review on bacterial and archaeal thermostable sulfur oxidoreductases (SORS)-an insight into the biochemical, molecular and in-silico structural comparative analysis of a neglected thermostable enzyme of industrial significance. Arch Microbiol 2022; 204:655. [PMID: 36175582 DOI: 10.1007/s00203-022-03256-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 09/08/2022] [Accepted: 09/12/2022] [Indexed: 11/02/2022]
Abstract
Diverse thermophilic microorganisms with the potential to withstand extreme physiological conditions have long been investigated and explored for human commercial benefit. Thermozymes with distinct functional and structural properties isolated from these thermophiles are known to have high thermostability without significant loss of specific enzyme activity. Thermophiles isolated and characterised from the thermophilic ecological niche of India are well documented. There is a plethora of work in the literature emphasising its industrial significance. However, in-depth knowledge of the thermophilic oxidoreductase group of enzymes (Oxizymes) is restricted. Sulfur Oxygenase Reductases or Sulfur Oxygen-Reductases (SORs) are a group of thermophilic oxizymes reported predominantly from thermophilic and mesophilic archaea and bacteria, which catalyse oxygen-dependent disproportionation reactions of elemental sulfur, producing sulfite, thiosulfate, and sulphide. There have been few reports on isolated and characterised SORs from the Indian geothermal niche. The review article will highlight the SORs reported till date with a concise overview of different archaeal and bacterial species producing the enzymes. Based on the literature available till date, characteristics including physico-chemical properties, amino acid sequence homology, conserved motifs and their 3D structure comparison have been discussed. In-silico sequence and structure level preliminary comparative analysis of various SORs has also been discussed. However, a few SORs whose structural information is not reported in the protein data bank have been modelled to enrich our analysis.
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Affiliation(s)
- Nirmalya Pal
- University Institute of Biotechnology, Chandigarh University, Gharuan, Mohali, Punjab, 140413, India
| | - Sanjana Sinha
- NMR Micro-Imaging and Spectroscopy Laboratory, Centre for Cellular and Molecular Biology, Uppal Rd, IICT Colony, Habsiguda, Hyderabad, 500007, Telangana, India
| | - Shivani
- University Institute of Biotechnology, Chandigarh University, Gharuan, Mohali, Punjab, 140413, India
| | - Mitun Chakraborty
- Department of Biotechnology Engineering and Food Technology, University Institute of Engineering, Chandigarh University, Gharuan, Mohali, Punjab, 140413, India.
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7
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Ferreira P, Fernandes P, Ramos M. The archaeal non-heme iron-containing Sulfur Oxygenase Reductase. Coord Chem Rev 2022. [DOI: 10.1016/j.ccr.2021.214358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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8
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Liu LJ, Jiang Z, Wang P, Qin YL, Xu W, Wang Y, Liu SJ, Jiang CY. Physiology, Taxonomy, and Sulfur Metabolism of the Sulfolobales, an Order of Thermoacidophilic Archaea. Front Microbiol 2021; 12:768283. [PMID: 34721370 PMCID: PMC8551704 DOI: 10.3389/fmicb.2021.768283] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 09/22/2021] [Indexed: 11/13/2022] Open
Abstract
The order Sulfolobales (phylum Crenarchaeota) is a group of thermoacidophilic archaea. The first member of the Sulfolobales was discovered in 1972, and current 23 species are validly named under the International Code of Nomenclature of Prokaryotes. The majority of members of the Sulfolobales is obligately or facultatively chemolithoautotrophic. When they grow autotrophically, elemental sulfur or reduced inorganic sulfur compounds are their energy sources. Therefore, sulfur metabolism is the most important physiological characteristic of the Sulfolobales. The functions of some enzymes and proteins involved in sulfur reduction, sulfur oxidation, sulfide oxidation, thiosulfate oxidation, sulfite oxidation, tetrathionate hydrolysis, and sulfur trafficking have been determined. In this review, we describe current knowledge about the physiology, taxonomy, and sulfur metabolism of the Sulfolobales, and note future challenges in this field.
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Affiliation(s)
- Li-Jun Liu
- School of Basic Medical Science, the Xi'an Key Laboratory of Pathogenic Microorganism and Tumor Immunity, Xi'an Medical University, Xi'an, China.,Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, China
| | - Zhen Jiang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Pei Wang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Ya-Ling Qin
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Wen Xu
- School of Basic Medical Science, the Xi'an Key Laboratory of Pathogenic Microorganism and Tumor Immunity, Xi'an Medical University, Xi'an, China.,Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, China
| | - Yang Wang
- School of Basic Medical Science, the Xi'an Key Laboratory of Pathogenic Microorganism and Tumor Immunity, Xi'an Medical University, Xi'an, China.,Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, China
| | - Shuang-Jiang Liu
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Cheng-Ying Jiang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
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9
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Willard DJ, Kelly RM. Intersection of Biotic and Abiotic Sulfur Chemistry Supporting Extreme Microbial Life in Hot Acid. J Phys Chem B 2021; 125:5243-5257. [PMID: 33979170 PMCID: PMC10562994 DOI: 10.1021/acs.jpcb.1c02102] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Microbial life on Earth exists within wide ranges of temperature, pressure, pH, salinity, radiation, and water activity. Extreme thermoacidophiles, in particular, are microbes found in hot, acidic biotopes laden with heavy metals and reduced inorganic sulfur species. As chemolithoautotrophs, they thrive in the absence of organic carbon, instead using sulfur and metal oxidation to fuel their bioenergetic needs, while incorporating CO2 as a carbon source. Metal oxidation by these microbes takes place extracellularly, mediated by membrane-associated oxidase complexes. In contrast, sulfur oxidation involves extracellular, membrane-associated, and cytoplasmic biotransformations, which intersect with abiotic sulfur chemistry. This novel lifestyle has been examined in the context of early aerobic life on this planet, but it is also interesting when considering the prospects of life, now or previously, on other solar bodies. Here, extreme thermoacidophily (growth at pH below 4.0, temperature above 55 °C), a characteristic of species in the archaeal order Sulfolobales, is considered from the perspective of sulfur chemistry, both biotic and abiotic, as it relates to microbial bioenergetics. Current understanding of the mechanisms involved are reviewed which are further expanded through recent experimental results focused on imparting sulfur oxidation capacity on a natively nonsulfur oxidizing extremely thermoacidophilic archaeon, Sulfolobus acidocaldarius, through metabolic engineering.
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Affiliation(s)
- Daniel J. Willard
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695
| | - Robert M. Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695
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10
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Kanao T, Hase N, Nakayama H, Yoshida K, Nishiura K, Kosaka M, Kamimura K, Hirano Y, Tamada T. Reaction mechanism of tetrathionate hydrolysis based on the crystal structure of tetrathionate hydrolase from Acidithiobacillus ferrooxidans. Protein Sci 2021; 30:328-338. [PMID: 33103311 PMCID: PMC7784748 DOI: 10.1002/pro.3984] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 10/21/2020] [Accepted: 10/23/2020] [Indexed: 11/10/2022]
Abstract
Tetrathionate hydrolase (4THase) plays an important role in dissimilatory sulfur oxidation in the acidophilic iron- and sulfur-oxidizing bacterium Acidithiobacillus ferrooxidans. The structure of recombinant 4THase from A. ferrooxidans (Af-Tth) was determined by X-ray crystallography to a resolution of 1.95 Å. Af-Tth is a homodimer, and its monomer structure exhibits an eight-bladed β-propeller motif. Two insertion loops participate in dimerization, and one loop forms a cavity with the β-propeller region. We observed unexplained electron densities in this cavity of the substrate-soaked structure. The anomalous difference map generated using diffraction data collected at a wavelength of 1.9 Å indicated the presence of polymerized sulfur atoms. Asp325, a highly conserved residue among 4THases, was located near the polymerized sulfur atoms. 4THase activity was completely abolished in the site-specific Af-Tth D325N variant, suggesting that Asp325 plays a crucial role in the first step of tetrathionate hydrolysis. Considering that the Af-Tth reaction occurs only under acidic pH, Asp325 acts as an acid for the tetrathionate hydrolysis reaction. The polymerized sulfur atoms in the active site cavity may represent the intermediate product in the subsequent step.
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Affiliation(s)
- Tadayoshi Kanao
- Department of Biofunctional Chemistry, Division of Agricultural and Life Science, Graduate School of Environmental and Life ScienceOkayama UniversityOkayamaJapan
| | - Naruki Hase
- Department of Biofunctional Chemistry, Division of Agricultural and Life Science, Graduate School of Environmental and Life ScienceOkayama UniversityOkayamaJapan
| | - Hisayuki Nakayama
- Department of Biofunctional Chemistry, Division of Agricultural and Life Science, Graduate School of Environmental and Life ScienceOkayama UniversityOkayamaJapan
| | - Kyoya Yoshida
- Department of Biofunctional Chemistry, Division of Agricultural and Life Science, Graduate School of Environmental and Life ScienceOkayama UniversityOkayamaJapan
| | - Kazumi Nishiura
- Department of Biofunctional Chemistry, Division of Agricultural and Life Science, Graduate School of Environmental and Life ScienceOkayama UniversityOkayamaJapan
| | - Megumi Kosaka
- Department of Instrumental Analysis, Advanced Science Research CenterOkayama UniversityOkayamaJapan
| | - Kazuo Kamimura
- Department of Biofunctional Chemistry, Division of Agricultural and Life Science, Graduate School of Environmental and Life ScienceOkayama UniversityOkayamaJapan
| | - Yu Hirano
- Institute for Quantum Life ScienceNational Institutes for Quantum and Radiological Science and TechnologyTokaiJapan
| | - Taro Tamada
- Institute for Quantum Life ScienceNational Institutes for Quantum and Radiological Science and TechnologyTokaiJapan
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11
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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. JOURNAL OF STRUCTURAL BIOLOGY-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] [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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12
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Zeldes BM, Loder AJ, Counts JA, Haque M, Widney KA, Keller LM, Albers S, Kelly RM. Determinants of sulphur chemolithoautotrophy in the extremely thermoacidophilicSulfolobales. Environ Microbiol 2019; 21:3696-3710. [DOI: 10.1111/1462-2920.14712] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 06/04/2019] [Accepted: 06/09/2019] [Indexed: 11/29/2022]
Affiliation(s)
- Benjamin M. Zeldes
- Department of Chemical and Biomolecular EngineeringNorth Carolina State University Raleigh NC 27695‐7905 USA
| | - Andrew J. Loder
- Department of Chemical and Biomolecular EngineeringNorth Carolina State University Raleigh NC 27695‐7905 USA
| | - James A. Counts
- Department of Chemical and Biomolecular EngineeringNorth Carolina State University Raleigh NC 27695‐7905 USA
| | - Mashkurul Haque
- Department of Chemical and Biomolecular EngineeringNorth Carolina State University Raleigh NC 27695‐7905 USA
| | - Karl A. Widney
- Department of Chemical and Biomolecular EngineeringNorth Carolina State University Raleigh NC 27695‐7905 USA
| | - Lisa M. Keller
- Department of Chemical and Biomolecular EngineeringNorth Carolina State University Raleigh NC 27695‐7905 USA
| | - Sonja‐Verena Albers
- Institute of Biology II – MicrobiologyUniversity of Freiburg Freiburg Germany
| | - Robert M. Kelly
- Department of Chemical and Biomolecular EngineeringNorth Carolina State University Raleigh NC 27695‐7905 USA
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13
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Amenabar MJ, Shock EL, Roden EE, Peters JW, Boyd ES. Microbial substrate preference dictated by energy demand, not supply. NATURE GEOSCIENCE 2017; 10:577-581. [PMID: 30944580 PMCID: PMC6443248 DOI: 10.1038/ngeo2978] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2017] [Accepted: 06/02/2017] [Indexed: 06/08/2023]
Abstract
Growth substrates that maximize energy yield are widely thought to be utilized preferentially by microorganisms. However, observed distributions of microorganisms and their activities often deviate from predictions based solely on thermodynamic considerations of substrate energy supply. Here we present observations of the bioenergetics and growth yields of a metabolically flexible, thermophilic strain of the archaeon Acidianus when grown autotrophically on minimal medium with hydrogen (H2) or elemental sulfur (S°) as an electron donor, and S° or ferric iron (Fe3+) as an electron acceptor. Thermodynamic calculations indicate that S°/Fe3+ and H2/Fe3+ yield three- and four-fold more energy per mol electron transferred, respectively, than the H2/S° couple. However, biomass yields in Acidianus cultures provided with H2/S° were eight-fold greater than when provided S°/Fe3+ or H2/Fe3+, indicating the H2/S° redox couple is preferred. Indeed, cells provided with all three growth substrates (H2, Fe3+, and S°) grew preferentially by reduction of S° with H2. We conclude that substrate preference is dictated by differences in the energy demand of electron transfer reactions in Acidianus when grown with different substrates, rather than substrate energy supply.
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Affiliation(s)
| | - Everett L. Shock
- School of Earth & Space Exploration and School of Molecular Sciences, Arizona State University, Tempe, Arizona
- NASA Astrobiology Institute, Mountain View, California
| | - Eric E. Roden
- Department of Geosciences, University of Wisconsin, Madison, Wisconsin
- NASA Astrobiology Institute, Mountain View, California
| | - John W. Peters
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana
| | - Eric S. Boyd
- Department of Microbiology and Immunology, Montana State University, Bozeman, Montana
- NASA Astrobiology Institute, Mountain View, California
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14
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Counts JA, Zeldes BM, Lee LL, Straub CT, Adams MWW, Kelly RM. Physiological, metabolic and biotechnological features of extremely thermophilic microorganisms. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2017; 9. [PMID: 28206708 DOI: 10.1002/wsbm.1377] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2016] [Revised: 11/23/2016] [Accepted: 11/30/2016] [Indexed: 12/12/2022]
Abstract
The current upper thermal limit for life as we know it is approximately 120°C. Microorganisms that grow optimally at temperatures of 75°C and above are usually referred to as 'extreme thermophiles' and include both bacteria and archaea. For over a century, there has been great scientific curiosity in the basic tenets that support life in thermal biotopes on earth and potentially on other solar bodies. Extreme thermophiles can be aerobes, anaerobes, autotrophs, heterotrophs, or chemolithotrophs, and are found in diverse environments including shallow marine fissures, deep sea hydrothermal vents, terrestrial hot springs-basically, anywhere there is hot water. Initial efforts to study extreme thermophiles faced challenges with their isolation from difficult to access locales, problems with their cultivation in laboratories, and lack of molecular tools. Fortunately, because of their relatively small genomes, many extreme thermophiles were among the first organisms to be sequenced, thereby opening up the application of systems biology-based methods to probe their unique physiological, metabolic and biotechnological features. The bacterial genera Caldicellulosiruptor, Thermotoga and Thermus, and the archaea belonging to the orders Thermococcales and Sulfolobales, are among the most studied extreme thermophiles to date. The recent emergence of genetic tools for many of these organisms provides the opportunity to move beyond basic discovery and manipulation to biotechnologically relevant applications of metabolic engineering. WIREs Syst Biol Med 2017, 9:e1377. doi: 10.1002/wsbm.1377 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- James A Counts
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Benjamin M Zeldes
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Laura L Lee
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Christopher T Straub
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
| | - Michael W W Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, USA
| | - Robert M Kelly
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC, USA
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15
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Engineering the residual side chains of HAP phytases to improve their pepsin resistance and catalytic efficiency. Sci Rep 2017; 7:42133. [PMID: 28186144 PMCID: PMC5301473 DOI: 10.1038/srep42133] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 01/06/2017] [Indexed: 11/08/2022] Open
Abstract
Strong resistance to proteolytic attack is important for feed enzymes. Here, we selected three predicted pepsin cleavage sites, L99, L162, and E230 (numbering from the initiator M of premature proteins), in pepsin-sensitive HAP phytases YkAPPA from Yersinia kristensenii and YeAPPA from Y. enterocolitica, which corresponded to L99, V162, and D230 in pepsin-resistant YrAPPA from Y. rohdei. We constructed mutants with different side chain structures at these sites using site-directed mutagenesis and produced all enzymes in Escherichia coli for catalytic and biochemical characterization. The substitutions E230G/A/P/R/S/T/D, L162G/A/V, L99A, L99A/L162G, and L99A/L162G/E230G improved the pepsin resistance. Moreover, E230G/A and L162G/V conferred enhanced pepsin resistance on YkAPPA and YeAPPA, increased their catalytic efficiency 1.3–2.4-fold, improved their stability at 60 °C and pH 1.0–2.0 and alleviated inhibition by metal ions. In addition, E230G increased the ability of YkAPPA and YeAPPA to hydrolyze phytate from corn meal at a high pepsin concentration and low pH, which indicated that optimization of the pepsin cleavage site side chains may enhance the pepsin resistance, improve the stability at acidic pH, and increase the catalytic activity. This study proposes an efficient approach to improve enzyme performance in monogastric animals fed feed with a high phytate content.
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16
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A Sulfur Oxygenase from the Haloalkaliphilic Bacterium Thioalkalivibrio paradoxus with Atypically Low Reductase Activity. J Bacteriol 2017; 199:JB.00675-16. [PMID: 27920296 DOI: 10.1128/jb.00675-16] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2016] [Accepted: 11/28/2016] [Indexed: 01/26/2023] Open
Abstract
Sequence comparisons showed that the sulfur oxygenase reductase (SOR) of the haloalkaliphilic bacterium Thioalkalivibrio paradoxus Arh 1 (TpSOR) is branching deeply within dendrograms of these proteins (29 to 34% identity). A synthetic gene encoding TpSOR expressed in Escherichia coli resulted in a protein 14.7 ± 0.9 nm in diameter and an apparent molecular mass of 556 kDa. Sulfite and thiosulfate were formed from elemental sulfur in a temperature range of 10 to 98°C (optimum temperature ≈ 80°C) and a pH range of 6 to 11.5 (optimum pH ≈ 9; 308 ± 78 U/mg of protein). Sulfide formation had a maximum specific activity of 0.03 U/mg, or <1% of the corresponding activity of other SORs. Hence, reductase activity seems not to be an integral part of the reaction mechanism. TpSOR was most active at NaCl or glycine betaine concentrations of 0 to 1 M, although 0.2% of the maximal activity was detected even at 5 M NaCl and 4 M betaine. The melting point of TpSOR was close to 80°C, when monitored by circular dichroism spectroscopy or differential scanning fluorimetry; however, the denaturation kinetics were slow: 55% of the residual activity remained after 25 min of incubation at 80°C. Site-directed mutagenesis showed that the active-site residue Cys44 is essential for activity, whereas alanine mutants of the two other conserved cysteines retained about 0.5% residual activity. A model of the sulfur metabolism in T. paradoxus is discussed. IMPORTANCE Sulfur oxygenase reductases (SORs) are the only enzymes catalyzing an oxygen-dependent disproportionation of elemental sulfur and/or polysulfides to sulfite, thiosulfate, and hydrogen sulfide. SORs are known from mesophilic and extremophilic archaea and bacteria. All SORs seem to form highly thermostable 24-subunit hollow spheres. They carry a low-potential mononuclear nonheme iron in the active site and an indispensable cysteine; however, their exact reaction mechanisms are unknown. Typically, the reductase activity of SORs is in the range of 5 to 50% of the oxygenase activity, but mutagenesis studies had so far failed to identify residues crucial for the reductase reaction. We describe here the first SOR, which is almost devoid of the reductase reaction and which comes from a haloalkaliphilic bacterium.
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17
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Acharya G, Kaur G, Subramanian S. Evolutionary relationships between heme-binding ferredoxin α + β barrels. BMC Bioinformatics 2016; 17:168. [PMID: 27089923 PMCID: PMC4835899 DOI: 10.1186/s12859-016-1033-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 04/12/2016] [Indexed: 01/19/2023] Open
Abstract
BACKGROUND The α + β barrel superfamily of the ferredoxin-like fold consists of a functionally diverse group of evolutionarily related proteins. The barrel architecture of these proteins is formed by either homo-/hetero-dimerization or duplication and fusion of ferredoxin-like domains. Several members of this superfamily bind heme in order to carry out their functions. RESULTS We analyze the heme-binding sites in these proteins as well as their barrel topologies. Our comparative structural analysis of these heme-binding barrels reveals two distinct modes of packing of the ferredoxin-like domains to constitute the α + β barrel, which is typified by the Type-1/IsdG-like and Type-2/OxdA-like proteins, respectively. We examine the heme-binding pockets and explore the versatility of the α + β barrels ability to accommodate heme or heme-related moieties, such as siroheme, in at least three different sites, namely, the mode seen in IsdG/OxdA, Cld/DyP/EfeB/HemQ and siroheme decarboxylase barrels. CONCLUSIONS Our study offers insights into the plausible evolutionary relationships between the two distinct barrel packing topologies and relate the observed heme-binding sites to these topologies.
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Affiliation(s)
- Giriraj Acharya
- CSIR-Institute of Microbial Technology (IMTECH), Sector 39-A, Chandigarh, India
| | - Gurmeet Kaur
- CSIR-Institute of Microbial Technology (IMTECH), Sector 39-A, Chandigarh, India
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18
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Celis AI, DuBois JL. Substrate, product, and cofactor: The extraordinarily flexible relationship between the CDE superfamily and heme. Arch Biochem Biophys 2015; 574:3-17. [PMID: 25778630 PMCID: PMC4414885 DOI: 10.1016/j.abb.2015.03.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Revised: 03/06/2015] [Accepted: 03/08/2015] [Indexed: 12/21/2022]
Abstract
PFam Clan 0032, also known as the CDE superfamily, is a diverse group of at least 20 protein families sharing a common α,β-barrel domain. Of these, six different groups bind heme inside the barrel's interior, using it alternately as a cofactor, substrate, or product. Focusing on these six, an integrated picture of structure, sequence, taxonomy, and mechanism is presented here, detailing how a single structural motif might be able to mediate such an array of functions with one of nature's most important small molecules.
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Affiliation(s)
- Arianna I Celis
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, United States
| | - Jennifer L DuBois
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, United States.
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19
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Kanao T, Nakayama H, Kato M, Kamimura K. The sole cysteine residue (Cys301) of tetrathionate hydrolase from Acidithiobacillus ferrooxidans does not play a role in enzyme activity. Biosci Biotechnol Biochem 2014; 78:2030-5. [PMID: 25144400 DOI: 10.1080/09168451.2014.948374] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Cysteine residues are absolutely indispensable for the reactions of almost all enzymes involved in the dissimilatory oxidation pathways of reduced inorganic sulfur compounds. Tetrathionate hydrolase from the acidophilic iron- and sulfur-oxidizing bacterium Acidithiobacillus ferrooxidans (Af-Tth) catalyzes tetrathionate hydrolysis to generate elemental sulfur, thiosulfate, and sulfate. Af-Tth is a key enzyme in the dissimilatory sulfur oxidation pathway in this bacterium. Only one cysteine residue (Cys301) has been identified in the deduced amino acid sequence of the Af-Tth gene. In order to clarify the role of the sole cysteine residue, a site-specific mutant enzyme (C301A) was generated. No difference was observed in the retention volumes of the wild-type and mutant Af-Tth enzymes by gel-filtration column chromatography, and surprisingly the enzyme activities measured in the cysteine-deficient and wild-type enzymes were the same. These results suggest that the sole cysteine residue (Cys301) in Af-Tth is involved in neither the tetrathionate hydrolysis reaction nor the subunit assembly. Af-Tth may thus have a novel cysteine-independent reaction mechanism.
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Affiliation(s)
- Tadayoshi Kanao
- a Department of Biofunctional Chemistry, Division of Agricultural and Life Science, Graduate School of Environmental and Life Science , Okayama University , Okayama , Japan
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20
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Souness RJ, Kleffmann T, Tchesnokov EP, Wilbanks SM, Jameson GB, Jameson GNL. Mechanistic implications of persulfenate and persulfide binding in the active site of cysteine dioxygenase. Biochemistry 2013; 52:7606-17. [PMID: 24084026 DOI: 10.1021/bi400661a] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Describing the organization of substrates and substrate analogues in the active site of cysteine dioxygenase identifies potential intermediates in this critical yet poorly understood reaction, the oxidation of cysteine to cysteine sulfinic acid. The fortuitous formation of persulfides under crystallization conditions has allowed their binding in the active site of cysteine dioxygenase to be studied. The crystal structures of cysteine persulfide and 3-mercaptopropionic acid persulfide bound to iron(II) in the active site show that binding of the persulfide occurs via the distal sulfide and, in the case of the cysteine persulfide, the amine also binds. Persulfide was detected by mass spectrometry in both the crystal and the drop, suggesting its origin is chemical rather than enzymatic. A mechanism involving the formation of the relevant disulfide from sulfide produced by hydrolysis of dithionite is proposed. In comparison, persulfenate {observed bound to cysteine dioxygenase [Simmons, C. R., et al. (2008) Biochemistry 47, 11390]} is shown through mass spectrometry to occur only in the crystal and not in the surrounding drop, suggesting that in the crystalline state the persulfenate does not lie on the reaction pathway. Stabilization of both the persulfenate and the persulfides does, however, suggest the position in which dioxygen binds during catalysis.
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Affiliation(s)
- Richard J Souness
- Department of Chemistry and MacDiarmid Institute for Advanced Materials and Nanotechnology and ‡Department of Biochemistry, University of Otago , P.O. Box 56, Dunedin 9054, New Zealand
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21
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Dopson M, Johnson DB. Biodiversity, metabolism and applications of acidophilic sulfur-metabolizing microorganisms. Environ Microbiol 2012; 14:2620-31. [PMID: 22510111 DOI: 10.1111/j.1462-2920.2012.02749.x] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Extremely acidic, sulfur-rich environments can be natural, such as solfatara fields in geothermal and volcanic areas, or anthropogenic, such as acid mine drainage waters. Many species of acidophilic bacteria and archaea are known to be involved in redox transformations of sulfur, using elemental sulfur and inorganic sulfur compounds as electron donors or acceptors in reactions involving between one and eight electrons. This minireview describes the nature and origins of acidic, sulfur-rich environments, the biodiversity of sulfur-metabolizing acidophiles, and how sulfur is metabolized and assimilated by acidophiles under aerobic and anaerobic conditions. Finally, existing and developing technologies that harness the abilities of sulfur-oxidizing and sulfate-reducing acidophiles to extract and capture metals, and to remediate sulfur-polluted waste waters are outlined.
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Affiliation(s)
- Mark Dopson
- School of Natural Sciences, Linnaeus University, Kalmar, Sweden
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The sulfur oxygenase reductase from the mesophilic bacterium Halothiobacillus neapolitanus is a highly active thermozyme. J Bacteriol 2011; 194:677-85. [PMID: 22139503 DOI: 10.1128/jb.06531-11] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A biochemical, biophysical, and phylogenetic study of the sulfur oxygenase reductase (SOR) from the mesophilic gammaproteobacterium Halothiobacillus neapolitanus (HnSOR) was performed in order to determine the structural and biochemical properties of the enzyme. SOR proteins from 14 predominantly chemolithoautotrophic bacterial and archaeal species are currently available in public databases. Sequence alignment and phylogenetic analysis showed that they form a coherent protein family. The HnSOR purified from Escherichia coli after heterologous gene expression had a temperature range of activity of 10 to 99°C with an optimum at 80°C (42 U/mg protein). Sulfite, thiosulfate, and hydrogen sulfide were formed at various stoichiometries in a range between pH 5.4 and 11 (optimum pH 8.4). Circular dichroism (CD) spectroscopy and dynamic light scattering showed that the HnSOR adopts secondary and quaternary structures similar to those of the 24-subunit enzyme from the hyperthermophile Acidianus ambivalens (AaSOR). The melting point of the HnSOR was ≈20°C lower than that of the AaSOR, when analyzed with CD-monitored thermal unfolding. Homology modeling showed that the secondary structure elements of single subunits are conserved. Subtle changes in the pores of the outer shell and increased flexibility might contribute to activity at low temperature. We concluded that the thermostability was the result of a rigid protein core together with the stabilizing effect of the 24-subunit hollow sphere.
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23
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Protze J, Müller F, Lauber K, Naß B, Mentele R, Lottspeich F, Kletzin A. An Extracellular Tetrathionate Hydrolase from the Thermoacidophilic Archaeon Acidianus Ambivalens with an Activity Optimum at pH 1. Front Microbiol 2011; 2:68. [PMID: 21747790 PMCID: PMC3128947 DOI: 10.3389/fmicb.2011.00068] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2011] [Accepted: 03/25/2011] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND The thermoacidophilic and chemolithotrophic archaeon Acidianus ambivalens is routinely grown with sulfur and CO(2)-enriched air. We had described a membrane-bound, tetrathionate (TT) forming thiosulfate:quinone oxidoreductase. Here we describe the first TT hydrolase (TTH) from Archaea. RESULTS A. ambivalens cells grown aerobically with TT as sole sulfur source showed doubling times of 9 h and final cell densities of up to 8 × 10(8)/ml. TTH activity (≈0.28 U/mg protein) was found in cell-free extracts of TT-grown but not of sulfur-grown cells. Differential fractionation of freshly harvested cells involving a pH shock showed that about 92% of the TTH activity was located in the pseudo-periplasmic fraction associated with the surface layer, while 7.3% and 0.3% were present in the soluble and membrane fractions, respectively. The enzyme was enriched 54-fold from the cytoplasmic fraction and 2.1-fold from the pseudo-periplasmic fraction. The molecular mass of the single subunit was 54 kDa. The optimal activity was at or above 95°C at pH 1. Neither PQQ nor divalent cations had a significant effect on activity. The gene (tth1) was identified following N-terminal sequencing of the protein. Northern hybridization showed that tth1 was transcribed in TT-grown cells in contrast to a second paralogous tth2 gene. The deduced amino acid sequences showed similarity to the TTH from Acidithiobacillus and other proteins from the PQQ dehydrogenase superfamily. It displayed a β-propeller structure when being modeled, however, important residues from the PQQ-binding site were absent. CONCLUSION The soluble, extracellular, and acidophilic TTH identified in TT-grown A. ambivalens cells is essential for TT metabolism during growth but not for the downstream processing of the TQO reaction products in S°-grown cells. The liberation of TTH by pH shock from otherwise intact cells strongly supports the pseudo-periplasm hypothesis of the S-layer of Archaea.
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Affiliation(s)
- Jonas Protze
- Institute of Microbiology and Genetics, Technische Universität DarmstadtDarmstadt, Germany
| | - Fabian Müller
- Institute of Microbiology and Genetics, Technische Universität DarmstadtDarmstadt, Germany
| | - Karin Lauber
- Institute of Microbiology and Genetics, Technische Universität DarmstadtDarmstadt, Germany
| | - Bastian Naß
- Institute of Microbiology and Genetics, Technische Universität DarmstadtDarmstadt, Germany
| | | | | | - Arnulf Kletzin
- Institute of Microbiology and Genetics, Technische Universität DarmstadtDarmstadt, Germany
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