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Tanabe TS, Bach E, D'Ermo G, Mohr MG, Hager N, Pfeiffer N, Guiral M, Dahl C. A cascade of sulfur transferases delivers sulfur to the sulfur-oxidizing heterodisulfide reductase-like complex. Protein Sci 2024; 33:e5014. [PMID: 38747384 PMCID: PMC11094781 DOI: 10.1002/pro.5014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2023] [Revised: 03/25/2024] [Accepted: 04/21/2024] [Indexed: 05/19/2024]
Abstract
A heterodisulfide reductase-like complex (sHdr) and novel lipoate-binding proteins (LbpAs) are central players of a wide-spread pathway of dissimilatory sulfur oxidation. Bioinformatic analysis demonstrate that the cytoplasmic sHdr-LbpA systems are always accompanied by sets of sulfur transferases (DsrE proteins, TusA, and rhodaneses). The exact composition of these sets may vary depending on the organism and sHdr system type. To enable generalizations, we studied model sulfur oxidizers from distant bacterial phyla, that is, Aquificota and Pseudomonadota. DsrE3C of the chemoorganotrophic Alphaproteobacterium Hyphomicrobium denitrificans and DsrE3B from the Gammaproteobacteria Thioalkalivibrio sp. K90mix, an obligate chemolithotroph, and Thiorhodospira sibirica, an obligate photolithotroph, are homotrimers that donate sulfur to TusA. Additionally, the hyphomicrobial rhodanese-like protein Rhd442 exchanges sulfur with both TusA and DsrE3C. The latter is essential for sulfur oxidation in Hm. denitrificans. TusA from Aquifex aeolicus (AqTusA) interacts physiologically with AqDsrE, AqLbpA, and AqsHdr proteins. This is particularly significant as it establishes a direct link between sulfur transferases and the sHdr-LbpA complex that oxidizes sulfane sulfur to sulfite. In vivo, it is unlikely that there is a strict unidirectional transfer between the sulfur-binding enzymes studied. Rather, the sulfur transferases form a network, each with a pool of bound sulfur. Sulfur flux can then be shifted in one direction or the other depending on metabolic requirements. A single pair of sulfur-binding proteins with a preferred transfer direction, such as a DsrE3-type protein towards TusA, may be sufficient to push sulfur into the sink where it is further metabolized or needed.
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Affiliation(s)
- Tomohisa Sebastian Tanabe
- Institut für Mikrobiologie & Biotechnologie, Rheinische Friedrich‐Wilhelms‐Universität BonnBonnGermany
- Division of Microbial EcologyUniversity of ViennaWienAustria
- Present address:
Division of Microbial Ecology, University of Vienna, Djerassiplatz 1 , A‐1030 WienKölnAustria
| | - Elena Bach
- Institut für Mikrobiologie & Biotechnologie, Rheinische Friedrich‐Wilhelms‐Universität BonnBonnGermany
| | - Giulia D'Ermo
- CNRS, Bioénergétique et Ingénierie des Protéines, Aix Marseille Université, IMMMarseilleFrance
| | - Marc Gregor Mohr
- Institut für Mikrobiologie & Biotechnologie, Rheinische Friedrich‐Wilhelms‐Universität BonnBonnGermany
| | - Natalie Hager
- Institut für Mikrobiologie & Biotechnologie, Rheinische Friedrich‐Wilhelms‐Universität BonnBonnGermany
| | - Niklas Pfeiffer
- Institut für Mikrobiologie & Biotechnologie, Rheinische Friedrich‐Wilhelms‐Universität BonnBonnGermany
- Present address:
Labor Dr. Wisplinghoff, Horbeller Str. 18‐20KölnGermany
| | - Marianne Guiral
- CNRS, Bioénergétique et Ingénierie des Protéines, Aix Marseille Université, IMMMarseilleFrance
| | - Christiane Dahl
- Institut für Mikrobiologie & Biotechnologie, Rheinische Friedrich‐Wilhelms‐Universität BonnBonnGermany
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Kümpel C, Grosser M, Tanabe TS, Dahl C. Fe/S proteins in microbial sulfur oxidation. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2024; 1871:119732. [PMID: 38631440 DOI: 10.1016/j.bbamcr.2024.119732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 02/26/2024] [Accepted: 04/04/2024] [Indexed: 04/19/2024]
Abstract
Iron-sulfur clusters serve as indispensable cofactors within proteins across all three domains of life. Fe/S clusters emerged early during the evolution of life on our planet and the biogeochemical cycle of sulfur is one of the most ancient and important element cycles. It is therefore no surprise that Fe/S proteins have crucial roles in the multiple steps of microbial sulfur metabolism. During dissimilatory sulfur oxidation in prokaryotes, Fe/S proteins not only serve as electron carriers in several steps, but also perform catalytic roles, including unprecedented reactions. Two cytoplasmic enzyme systems that oxidize sulfane sulfur to sulfite are of particular interest in this context: The rDsr pathway employs the reverse acting dissimilatory sulfite reductase rDsrAB as its key enzyme, while the sHdr pathway utilizes polypeptides resembling the HdrA, HdrB and HdrC subunits of heterodisulfide reductase from methanogenic archaea. Both pathways involve components predicted to bind unusual noncubane Fe/S clusters acting as catalysts for the formation of disulfide or sulfite. Mapping of Fe/S cluster machineries on the sulfur-oxidizing prokaryote tree reveals that ISC, SUF, MIS and SMS are all sufficient to meet the Fe/S cluster maturation requirements for operation of the sHdr or rDsr pathways. The sHdr pathway is dependent on lipoate-binding proteins that are assembled by a novel pathway, involving two Radical SAM proteins, namely LipS1 and LipS2. These proteins coordinate sulfur-donating auxiliary Fe/S clusters in atypical patterns by three cysteines and one histidine and act as lipoyl synthases by jointly inserting two sulfur atoms to an octanoyl residue. This article is part of a Special Issue entitled: Biogenesis and Function of Fe/S proteins.
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Affiliation(s)
- Carolin Kümpel
- Institut für Mikrobiologie & Biotechnologie, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
| | - Martina Grosser
- Institut für Mikrobiologie & Biotechnologie, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
| | - Tomohisa Sebastian Tanabe
- Institut für Mikrobiologie & Biotechnologie, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
| | - Christiane Dahl
- Institut für Mikrobiologie & Biotechnologie, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany.
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Wang T, Li X, Liu H, Liu H, Xia Y, Xun L. Microorganisms uptake zero-valent sulfur via membrane lipid dissolution of octasulfur and intracellular solubilization as persulfide. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 922:170504. [PMID: 38307292 DOI: 10.1016/j.scitotenv.2024.170504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 01/19/2024] [Accepted: 01/25/2024] [Indexed: 02/04/2024]
Abstract
Zero-valent sulfur, commonly utilized as a fertilizer or fungicide, is prevalent in various environmental contexts. Its most stable and predominant form, octasulfur (S8), plays a crucial role in microbial sulfur metabolism, either through oxidation or reduction. However, the mechanism underlying its cellular uptake remains elusive. We presented evidence that zero-valent sulfur was adsorbed to the cell surface and then dissolved into the membrane lipid layer as lipid-soluble S8 molecules, which reacted with cellular low-molecular thiols to form persulfide, e.g., glutathione persulfide (GSSH), in the cytoplasm. The process brought extracellular zero-valent sulfur into the cells. When persulfide dioxygenase is present in the cells, GSSH will be oxidized. Otherwise, GSSH will react with another glutathione (GSH) to produce glutathione disulfide (GSSG) and hydrogen sulfide (H2S). The mechanism is different from simple diffusion, as insoluble S8 becomes soluble GSSH after crossing the cytoplasmic membrane. The uptake process is limited by physical contact of insoluble zero-valent sulfur with microbial cells and the regeneration of cellular thiols. Our findings elucidate the cellular uptake mechanism of zero-valent sulfur, which provides critical information for its application in agricultural practices and the bioremediation of sulfur contaminants and heavy metals.
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Affiliation(s)
- Tianqi Wang
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China
| | - Xiaoju Li
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China
| | - Honglei Liu
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China
| | - Huaiwei Liu
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China
| | - Yongzhen Xia
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China.
| | - Luying Xun
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China; School of Molecular Biosciences, Washington State University, Pullman, WA 99164-7520, USA.
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Prioretti L, D’Ermo G, Infossi P, Kpebe A, Lebrun R, Bauzan M, Lojou E, Guigliarelli B, Giudici-Orticoni MT, Guiral M. Carbon Fixation in the Chemolithoautotrophic Bacterium Aquifex aeolicus Involves Two Low-Potential Ferredoxins as Partners of the PFOR and OGOR Enzymes. Life (Basel) 2023; 13:life13030627. [PMID: 36983784 PMCID: PMC10052474 DOI: 10.3390/life13030627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 02/21/2023] [Accepted: 02/22/2023] [Indexed: 02/27/2023] Open
Abstract
Aquifex aeolicus is a microaerophilic hydrogen- and sulfur -oxidizing bacterium that assimilates CO2 via the reverse tricarboxylic acid cycle (rTCA). Key enzymes of this pathway are pyruvate:ferredoxin oxidoreductase (PFOR) and 2-oxoglutarate:ferredoxin oxidoreductase (OGOR), which are responsible, respectively, for the reductive carboxylation of acetyl-CoA to pyruvate and of succinyl-CoA to 2-oxoglutarate, two energetically unfavorable reactions that require a strong reduction potential. We have confirmed, by biochemistry and proteomics, that A. aeolicus possesses a pentameric version of these enzyme complexes ((αβγδε)2) and that they are highly abundant in the cell. In addition, we have purified and characterized, from the soluble fraction of A. aeolicus, two low redox potential and oxygen-stable [4Fe-4S] ferredoxins (Fd6 and Fd7, E0 = −440 and −460 mV, respectively) and shown that they can physically interact and exchange electrons with both PFOR and OGOR, suggesting that they could be the physiological electron donors of the system in vivo. Shotgun proteomics indicated that all the enzymes assumed to be involved in the rTCA cycle are produced in the A. aeolicus cells. A number of additional enzymes, previously suggested to be part of a putative partial Wood-Ljungdahl pathway used for the synthesis of serine and glycine from CO2 were identified by mass spectrometry, but their abundance in the cell seems to be much lower than that of the rTCA cycle. Their possible involvement in carbon assimilation is discussed.
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Affiliation(s)
- Laura Prioretti
- CNRS, Bioénergétique et Ingénierie des Protéines, Aix Marseille Université, IMM, 13009 Marseille, France
| | - Giulia D’Ermo
- CNRS, Bioénergétique et Ingénierie des Protéines, Aix Marseille Université, IMM, 13009 Marseille, France
| | - Pascale Infossi
- CNRS, Bioénergétique et Ingénierie des Protéines, Aix Marseille Université, IMM, 13009 Marseille, France
| | - Arlette Kpebe
- CNRS, Bioénergétique et Ingénierie des Protéines, Aix Marseille Université, IMM, 13009 Marseille, France
| | - Régine Lebrun
- CNRS, Aix Marseille Université, IMM, 13009 Marseille, France
| | - Marielle Bauzan
- CNRS, Aix Marseille Université, IMM, 13009 Marseille, France
| | - Elisabeth Lojou
- CNRS, Bioénergétique et Ingénierie des Protéines, Aix Marseille Université, IMM, 13009 Marseille, France
| | - Bruno Guigliarelli
- CNRS, Bioénergétique et Ingénierie des Protéines, Aix Marseille Université, IMM, 13009 Marseille, France
| | | | - Marianne Guiral
- CNRS, Bioénergétique et Ingénierie des Protéines, Aix Marseille Université, IMM, 13009 Marseille, France
- Correspondence:
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A metabolic puzzle: Consumption of C 1 compounds and thiosulfate in Hyphomicrobium denitrificans X T. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2023; 1864:148932. [PMID: 36367491 DOI: 10.1016/j.bbabio.2022.148932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 10/17/2022] [Accepted: 10/24/2022] [Indexed: 11/09/2022]
Abstract
Many obligately heterotrophic methylotrophs oxidize thiosulfate as an additional electron source during growth on C1 compounds. Although two different pathways of thiosulfate oxidation are implemented in Hyphomicrobium denitrificans XT, a pronounced negative effect on growth rate is observed when it is cultured in the simultaneous presence of methanol and thiosulfate. In this model organism, periplasmic thiosulfate dehydrogenase TsdA catalyzes formation of the dead-end product tetrathionate. By reverse genetics we verified the second pathway that also starts in the periplasm where SoxXA catalyzes the oxidative fusion of thiosulfate to SoxYZ, from which sulfate is released by SoxB. Sulfane sulfur is then further oxidized in the cytoplasm by the sulfur-oxidizing heterodisulfide reductase-like system (sHdr) which is produced constitutively in a strain lacking the transcriptional repressor sHdrR. When exposed to thiosulfate, the ΔshdrR strain exhibited a strongly reduced growth rate even without thiosulfate in the pre-cultures. When grown on methanol, cells exhibit significantly increased NAD+/NADH ratios in the presence of thiosulfate. In contrast, thiosulfate did not exert any negative effect on growth rate or increase NAD+ levels during growth on formate. On both C1 substrates, excretion of up to 0.5 mM sulfite as an intermediate of thiosulfate (2 mM) oxidation was recorded. Sulfite is known to form adducts with pyrroloquinoline quinone, the cofactor of periplasmic methanol dehydrogenase. We rationalize that this causes specific inhibition of methanol degradation in the presence of thiosulfate while formate metabolism in the cytoplasm remains unaffected.
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Han S, Li Y, Gao H. Generation and Physiology of Hydrogen Sulfide and Reactive Sulfur Species in Bacteria. Antioxidants (Basel) 2022; 11:antiox11122487. [PMID: 36552695 PMCID: PMC9774590 DOI: 10.3390/antiox11122487] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 12/14/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022] Open
Abstract
Sulfur is not only one of the most abundant elements on the Earth, but it is also essential to all living organisms. As life likely began and evolved in a hydrogen sulfide (H2S)-rich environment, sulfur metabolism represents an early form of energy generation via various reactions in prokaryotes and has driven the sulfur biogeochemical cycle since. It has long been known that H2S is toxic to cells at high concentrations, but now this gaseous molecule, at the physiological level, is recognized as a signaling molecule and a regulator of critical biological processes. Recently, many metabolites of H2S, collectively called reactive sulfur species (RSS), have been gradually appreciated as having similar or divergent regulatory roles compared with H2S in living organisms, especially mammals. In prokaryotes, even in bacteria, investigations into generation and physiology of RSS remain preliminary and an understanding of the relevant biological processes is still in its infancy. Despite this, recent and exciting advances in the fields are many. Here, we discuss abiotic and biotic generation of H2S/RSS, sulfur-transforming enzymes and their functioning mechanisms, and their physiological roles as well as the sensing and regulation of H2S/RSS.
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Nguyen PM, Do PT, Pham YB, Doan TO, Nguyen XC, Lee WK, Nguyen DD, Vadiveloo A, Um MJ, Ngo HH. Roles, mechanism of action, and potential applications of sulfur-oxidizing bacteria for environmental bioremediation. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 852:158203. [PMID: 36044953 DOI: 10.1016/j.scitotenv.2022.158203] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2022] [Revised: 08/17/2022] [Accepted: 08/18/2022] [Indexed: 06/15/2023]
Abstract
Sulfur (S) is a crucial component in the environment and living organisms. This work is the first attempt to provide an overview and critical discussion on the roles, mechanisms, and environmental applications of sulfur-oxidizing bacteria (SOB). The findings reveal that key enzymes of SOB embarked on oxidation of sulfide, sulfite, thiosulfate, and elemental S. Conversion of reduced S compounds was oxidatively catalyzed by various enzymes (e.g. sulfide: quinone oxidoreductase, flavocytochrome c-sulfide dehydrogenase, dissimilatory sulfite reductase, heterodisulfide reductase-like proteins). Environmental applications of SOB discussed include detoxifying hydrogen sulfide, soil bioremediation, and wastewater treatment. SOB producing S0 engaged in biological S soil amendments (e.g. saline-alkali soil remediation, the oxidation of sulfide-bearing minerals). Biotreatment of H2S using SOB occurred under both aerobic and anaerobic conditions. Sulfide, nitrate, and sulfamethoxazole were removed through SOB suspension cultures and S0-based carriers. Finally, this work presented future perspectives on SOB development, including S0 recovery, SOB enrichment, field measurement and identification of sulfur compounds, and the development of mathematical simulation.
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Affiliation(s)
- Phuong Minh Nguyen
- Faculty of Environmental Sciences, University of Science, Vietnam National University, Hanoi, 334 Nguyen Trai, Thanh Xuan, Hanoi, Vietnam
| | - Phuc Thi Do
- Faculty of Biology, University of Science, Vietnam National University, Hanoi, 334 Nguyen Trai, Thanh Xuan, Hanoi, Vietnam; Key Laboratory of Enzyme and Protein Technology (KLEPT), University of Science, Vietnam National University, Hanoi, 334 Nguyen Trai, Thanh Xuan, Hanoi, Vietnam
| | - Yen Bao Pham
- Key Laboratory of Enzyme and Protein Technology (KLEPT), University of Science, Vietnam National University, Hanoi, 334 Nguyen Trai, Thanh Xuan, Hanoi, Vietnam
| | - Thi Oanh Doan
- Faculty of Environment, Ha Noi University of Natural Resources and Environment, No 41A, Phu Dien Street, Bac Tu Liem, Ha Noi, Vietnam
| | - Xuan Cuong Nguyen
- Center for Advanced Chemistry, Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam; Faculty of Environmental Chemical Engineering, Duy Tan University, Da Nang 550000, Vietnam.
| | - Woo Kul Lee
- Department of Chemical Engineering, Dankook University, 152 Jukjeonro, Yongin 16890, South Korea
| | - D Duc Nguyen
- Faculty of Environmental and Food Engineering, Nguyen Tat Thanh University, 300A Nguyen Tat Thanh, District 4, HCM City, 755414, Vietnam; Department of Environmental Energy Engineering, Kyonggi University, Suwon 16227, South Korea
| | - Ashiwin Vadiveloo
- Algae R & D Centre, Environmental and Conservation Sciences, College of Science, Health, Engineering and Education, 90 South Street, Murdoch, WA 6150, Australia
| | - Myoung-Jin Um
- Department of Civil Engineering, Kyonggi University, Suwon 16227, South Korea
| | - Huu Hao Ngo
- School of Civil and Environmental Engineering, University of Technology Sydney, Sydney, NWS 2007, Australia.
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Tanabe TS, Dahl C. HMS-S-S: a tool for the identification of sulfur metabolism-related genes and analysis of operon structures in genome and metagenome assemblies. Mol Ecol Resour 2022; 22:2758-2774. [PMID: 35579058 DOI: 10.1111/1755-0998.13642] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 04/25/2022] [Accepted: 05/11/2022] [Indexed: 11/26/2022]
Abstract
Sulfur compounds are used in a variety of biological processes including respiration and photosynthesis. Sulfide and sulfur compounds of intermediary oxidation state can serve as electron donors for lithotrophic growth while sulfate, thiosulfate and sulfur are used as electron acceptors in anaerobic respiration. The biochemistry underlying the manifold transformations of inorganic sulfur compounds occurring in sulfur metabolizing prokaryotes is astonishingly complex and knowledge about it has immensely increased over the last years. The advent of next-generation sequencing approaches as well as the significant increase of data availability in public databases has driven focus of environmental microbiology to probing the metabolic capacity of microbial communities by analysis of this sequence data. To facilitate these analyses, we created HMS-S-S, a comprehensive equivalogous hidden Markov model (HMM)-supported tool. Protein sequences related to sulfur compound oxidation, reduction, transport and intracellular transfer are efficiently detected and related enzymes involved in dissimilatory sulfur oxidation as opposed to sulfur compound reduction can be confidently distinguished. HMM search results are coupled to corresponding genes, which allows analysis of co-occurrence, synteny and genomic neighborhood. The HMMs were validated on an annotated test dataset and by cross-validation. We also proved its performance by exploring meta-assembled genomes isolated from samples from environments with active sulfur cycling, including members of the cable bacteria, novel Acidobacteria and assemblies from a sulfur-rich glacier, and were able to replicate and extend previous reports.
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Affiliation(s)
- Tomohisa Sebastian Tanabe
- Institut für Mikrobiologie & Biotechnologie, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
| | - Christiane Dahl
- Institut für Mikrobiologie & Biotechnologie, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
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Appel L, Willistein M, Dahl C, Ermler U, Boll M. Functional diversity of prokaryotic HdrA(BC) modules: Role in flavin-based electron bifurcation processes and beyond. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2021; 1862:148379. [PMID: 33460586 DOI: 10.1016/j.bbabio.2021.148379] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 01/08/2021] [Accepted: 01/11/2021] [Indexed: 10/22/2022]
Abstract
In methanogenic archaea, the archetypical complex of heterodisulfide reductase (HdrABC) and hydrogenase (MvhAGD) couples the endergonic reduction of CO2 by H2 to the exergonic reduction of the CoB-S-S-CoM heterodisulfide by H2 via flavin-based electron bifurcation. Presently known enzymes containing HdrA(BC)-like components play key roles in methanogenesis, acetogenesis, respiratory sulfate reduction, lithotrophic reduced sulfur compound oxidation, aromatic compound degradation, fermentations, and probably many further processes. This functional diversity is achieved by a modular architecture of HdrA(BC) enzymes, where a big variety of electron input/output modules may be connected either directly or via adaptor modules to the HdrA(BC) components. Many, but not all HdrA(BC) complexes are proposed to catalyse a flavin-based electron bifurcation/confurcation. Despite the availability of HdrA(BC) crystal structures, fundamental questions of electron transfer and energy coupling processes remain. Here, we address the common properties and functional diversity of HdrA(BC) core modules integrated into electron-transfer machineries of outstanding complexity.
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Affiliation(s)
- Lena Appel
- Fakultät für Biologie - Mikrobiologie, Universität Freiburg, Freiburg, Germany
| | - Max Willistein
- Fakultät für Biologie - Mikrobiologie, Universität Freiburg, Freiburg, Germany
| | - Christiane Dahl
- Institut für Mikrobiologie & Biotechnologie, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
| | - Ulrich Ermler
- Max-Planck-Institut für Biophysik, Frankfurt, Germany
| | - Matthias Boll
- Fakultät für Biologie - Mikrobiologie, Universität Freiburg, Freiburg, Germany.
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