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Huang S, Méheust R, Barquera B, Light SH. Versatile roles of protein flavinylation in bacterial extracyotosolic electron transfer. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.13.584918. [PMID: 38559090 PMCID: PMC10979944 DOI: 10.1101/2024.03.13.584918] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Bacteria perform diverse redox chemistries in the periplasm, cell wall, and extracellular space. Electron transfer for these extracytosolic activities is frequently mediated by proteins with covalently bound flavins, which are attached through post-translational flavinylation by the enzyme ApbE. Despite the significance of protein flavinylation to bacterial physiology, the basis and function of this modification remains unresolved. Here we apply genomic context analyses, computational structural biology, and biochemical studies to address the role of ApbE flavinylation throughout bacterial life. We find that ApbE flavinylation sites exhibit substantial structural heterogeneity. We identify two novel classes of flavinylation substrates that are related to characterized proteins with non-covalently bound flavins, providing evidence that protein flavinylation can evolve from a non-covalent flavoprotein precursor. We further find a group of structurally related flavinylation-associated cytochromes, including those with the domain of unknown function DUF4405, that presumably mediate electron transfer in the cytoplasmic membrane. DUF4405 homologs are widespread in bacteria and related to ferrosome iron storage organelle proteins that may facilitate iron redox cycling within ferrosomes. These studies reveal a complex basis for flavinylated electron transfer and highlight the discovery power of coupling comparative genomic analyses with high-quality structural models.
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Affiliation(s)
- Shuo Huang
- Duchossois Family Institute, University of Chicago, Chicago, IL, USA
- Department of Microbiology, University of Chicago, Chicago, IL, USA
| | - Raphaël Méheust
- Génomique Métabolique, CEA, Genoscope, Institut François Jacob, Université d’Évry, Université Paris-Saclay, CNRS, Evry, France
| | - Blanca Barquera
- Department of Biological Sciences, Department of Chemistry and Chemical Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute; Troy, NY
| | - Samuel H. Light
- Duchossois Family Institute, University of Chicago, Chicago, IL, USA
- Department of Microbiology, University of Chicago, Chicago, IL, USA
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2
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Tong Y, Rozeboom HJ, Loonstra MR, Wijma HJ, Fraaije MW. Characterization of two bacterial multi-flavinylated proteins harboring multiple covalent flavin cofactors. BBA ADVANCES 2023; 4:100097. [PMID: 37455753 PMCID: PMC10339131 DOI: 10.1016/j.bbadva.2023.100097] [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: 05/24/2023] [Revised: 06/27/2023] [Accepted: 07/03/2023] [Indexed: 07/18/2023] Open
Abstract
In recent years, studies have shown that a large number of bacteria secrete multi-flavinylated proteins. The exact roles and properties, of these extracellular flavoproteins that contain multiple covalently anchored FMN cofactors, are still largely unknown. Herein, we describe the biochemical and structural characterization of two multi-FMN-containing covalent flavoproteins, SaFMN3 from Streptomyces azureus and CbFMN4 from Clostridiaceae bacterium. Based on their primary structure, these proteins were predicted to contain three and four covalently tethered FMN cofactors, respectively. The genes encoding SaFMN3 and CbFMN4 were heterologously coexpressed with a flavin transferase (ApbE) in Escherichia coli, and could be purified by affinity chromatography in good yields. Both proteins were found to be soluble and to contain covalently bound FMN molecules. The SaFMN3 protein was studied in more detail and found to display a single redox potential (-184 mV) while harboring three covalently attached flavins. This is in line with the high sequence similarity when the domains of each flavoprotein are compared. The fully reduced form of SaFMN3 is able to use dioxygen as electron acceptor. Single domains from both proteins were expressed, purified and crystallized. The crystal structures were elucidated, which confirmed that the flavin cofactor is covalently attached to a threonine. Comparison of both crystal structures revealed a high similarity, even in the flavin binding pocket. Based on the crystal structure, mutants of the SaFMN3-D2 domain were designed to improve its fluorescence quantum yield by changing the microenvironment of the isoalloxazine moiety of the flavin cofactor. Residues that quench the flavin fluorescence were successfully identified. Our study reveals biochemical details of multi-FMN-containing proteins, contributing to a better understanding of their role in bacteria and providing leads to future utilization of these flavoprotein in biotechnology.
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3
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WANG M, ZHANG W, WANG N. Covalent flavoproteins: types, occurrence, biogenesis and catalytic mechanisms. Chin J Nat Med 2022; 20:749-760. [DOI: 10.1016/s1875-5364(22)60194-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2022] [Indexed: 11/03/2022]
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4
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Willow SY, Yuan M, Juárez O, Minh DDL. Electrostatics and water occlusion regulate covalently-bound flavin mononucleotide cofactors of Vibrio cholerae respiratory complex NQR. Proteins 2021; 89:1376-1385. [PMID: 34091964 DOI: 10.1002/prot.26158] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 05/20/2021] [Accepted: 06/01/2021] [Indexed: 12/20/2022]
Abstract
Proteins like NADH:ubiquinone oxidoreductase (NQR), an essential enzyme and ion pump in the physiology of several pathogenic bacteria, tightly regulate the redox properties of their cofactors. Although flavin mononucleotide (FMN) is fully reduced in aqueous solution, FMN in subunits B and C of NQR exclusively undergo one-electron transitions during its catalytic cycle. Here, we perform ab initio calculations and molecular dynamics simulations to elucidate the mechanisms that regulate the redox state of FMN in NQR. QM/MM calculations show that binding site electrostatics disfavor anionic forms of FMNH2 , but permit a neutral form of the fully reduced flavin. The potential energy surface is unaffected by covalent bonding between FMN and threonine. Molecular dynamics simulations show that the FMN binding sites are inaccessible by water, suggesting that further reductions of the cofactors are limited or prohibited by the availability of water and other proton donors. These findings provide a deeper understanding of the mechanisms used by NQR to regulate electron transfer through the cofactors and perform its physiologic role. They also provide the first, to our knowledge, evidence of the simple concept that proteins regulate flavin redox states via water occlusion.
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Affiliation(s)
- Soohaeng Yoo Willow
- Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois, USA
| | - Ming Yuan
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois, USA
| | - Oscar Juárez
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois, USA
| | - David D L Minh
- Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois, USA
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5
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Specific chemical modification explores dynamic structure of the NqrB subunit in Na +-pumping NADH-ubiquinone oxidoreductase from Vibrio cholerae. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2021; 1862:148432. [PMID: 33932367 DOI: 10.1016/j.bbabio.2021.148432] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 02/28/2021] [Accepted: 04/20/2021] [Indexed: 12/28/2022]
Abstract
The Na+-pumping NADH-ubiquinone oxidoreductase (Na+-NQR) is a main ion transporter in many pathogenic bacteria. We previously proposed that N-terminal stretch of the NqrB subunit plays an important role in regulating the ubiquinone reaction at the adjacent NqrA subunit in Vibrio cholerae Na+-NQR. However, since approximately three quarters of the stretch (NqrB-Met1-Pro37) was not modeled in an earlier crystallographic study, its structure and function remain unknown. If we can develop a method that enables pinpoint modification of this stretch by functional chemicals (such as spin probes), it could lead to new ways to investigate the unsettled issues. As the first step to this end, we undertook to specifically attach an alkyne group to a lysine located in the stretch via protein-ligand affinity-driven substitution using synthetic ligands NAS-K1 and NAS-K2. The alkyne, once attached, can serve as an "anchor" for connecting functional chemicals via convenient click chemistry. After a short incubation of isolated Na+-NQR with these ligands, alkyne was predominantly incorporated into NqrB. Proteomic analyses in combination with mutagenesis of predicted target lysines revealed that alkyne attaches to NqrB-Lys22 located at the nonmodeled region of the stretch. This study not only achieved the specific modification initially aimed for but also provided valuable information about positioning of the nonmodeled region. For example, the fact that hydrophobic NAS-Ks come into contact with NqrB-Lys22 suggests that the nonmodeled region may orient toward the membrane phase rather than protruding into cytoplasmic medium. This conformation may be essential for regulating the ubiquinone reaction in the adjacent NqrA.
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6
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Bennett SP, Torres MJ, Soriano-Laguna MJ, Richardson DJ, Gates AJ, Le Brun NE. nosX is essential for whole-cell N 2O reduction in Paracoccus denitrificans but not for assembly of copper centres of nitrous oxide reductase. MICROBIOLOGY-SGM 2020; 166:909-917. [PMID: 32886603 PMCID: PMC7660919 DOI: 10.1099/mic.0.000955] [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] [Indexed: 12/22/2022]
Abstract
Nitrous oxide (N2O) is a potent greenhouse gas that is produced naturally as an intermediate during the process of denitrification carried out by some soil bacteria. It is consumed by nitrous oxide reductase (N2OR), the terminal enzyme of the denitrification pathway, which catalyses a reduction reaction to generate dinitrogen. N2OR contains two important copper cofactors (CuA and CuZ centres) that are essential for activity, and in copper-limited environments, N2OR fails to function, contributing to rising levels of atmospheric N2O and a major environmental challenge. Here we report studies of nosX, one of eight genes in the nos cluster of the soil dwelling α-proteobaterium Paraccocus denitrificans. A P. denitrificans ΔnosX deletion mutant failed to reduce N2O under both copper-sufficient and copper-limited conditions, demonstrating that NosX plays an essential role in N2OR activity. N2OR isolated from nosX-deficient cells was found to be unaffected in terms of the assembly of its copper cofactors, and to be active in in vitro assays, indicating that NosX is not required for the maturation of the enzyme; in particular, it plays no part in the assembly of either of the CuA and CuZ centres. Furthermore, quantitative Reverse Transcription PCR (qRT-PCR) studies showed that NosX does not significantly affect the expression of the N2OR-encoding nosZ gene. NosX is a homologue of the FAD-binding protein ApbE from Pseudomonas stutzeri, which functions in the flavinylation of another N2OR accessory protein, NosR. Thus, it is likely that NosX is a system-specific maturation factor of NosR, and so is indirectly involved in maintaining the reaction cycle of N2OR and cellular N2O reduction.
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Affiliation(s)
- Sophie P Bennett
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Maria J Torres
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Manuel J Soriano-Laguna
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - David J Richardson
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Andrew J Gates
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Nick E Le Brun
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
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7
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Masuya T, Sano Y, Tanaka H, Butler NL, Ito T, Tosaki T, Morgan JE, Murai M, Barquera B, Miyoshi H. Inhibitors of a Na +-pumping NADH-ubiquinone oxidoreductase play multiple roles to block enzyme function. J Biol Chem 2020; 295:12739-12754. [PMID: 32690607 DOI: 10.1074/jbc.ra120.014229] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 07/18/2020] [Indexed: 11/06/2022] Open
Abstract
The Na+-pumping NADH-ubiquinone (UQ) oxidoreductase (Na+-NQR) is present in the respiratory chain of many pathogenic bacteria and is thought to be a promising antibiotic target. Whereas many details of Na+-NQR structure and function are known, the mechanisms of action of potent inhibitors is not well-understood; elucidating the mechanisms would not only advance drug design strategies but might also provide insights on a terminal electron transfer from riboflavin to UQ. To this end, we performed photoaffinity labeling experiments using photoreactive derivatives of two known inhibitors, aurachin and korormicin, on isolated Vibrio cholerae Na+-NQR. The inhibitors labeled the cytoplasmic surface domain of the NqrB subunit including a protruding N-terminal stretch, which may be critical to regulate the UQ reaction in the adjacent NqrA subunit. The labeling was blocked by short-chain UQs such as ubiquinone-2. The photolabile group (2-aryl-5-carboxytetrazole (ACT)) of these inhibitors reacts with nucleophilic amino acids, so we tested mutations of nucleophilic residues in the labeled region of NqrB, such as Asp49 and Asp52 (to Ala), and observed moderate decreases in labeling yields, suggesting that these residues are involved in the interaction with ACT. We conclude that the inhibitors interfere with the UQ reaction in two ways: the first is blocking structural rearrangements at the cytoplasmic interface between NqrA and NqrB, and the second is the direct obstruction of UQ binding at this interfacial area. Unusual competitive behavior between the photoreactive inhibitors and various competitors corroborates our previous proposition that there may be two inhibitor binding sites in Na+-NQR.
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Affiliation(s)
- Takahiro Masuya
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Yuki Sano
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Hinako Tanaka
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | | | | | - Tatsuhiko Tosaki
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Joel E Morgan
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Masatoshi Murai
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Blanca Barquera
- Department of Biological Science and.,Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Hideto Miyoshi
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
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8
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Bertsova YV, Serebryakova MV, Anashkin VA, Baykov AA, Bogachev AV. Mutational analysis of the flavinylation and binding motifs in two protein targets of the flavin transferase ApbE. FEMS Microbiol Lett 2019; 366:5675630. [DOI: 10.1093/femsle/fnz252] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2019] [Accepted: 12/12/2019] [Indexed: 12/12/2022] Open
Abstract
ABSTRACT
Many flavoproteins belonging to three domain types contain an FMN residue linked through a phosphoester bond to a threonine or serine residue found in a conserved seven-residue motif. The flavinylation reaction is catalyzed by a specific enzyme, ApbE, which uses FAD as a substrate. To determine the structural requirements of the flavinylation reaction, we examined the effects of single substitutions in the flavinylation motif of Klebsiella pneumoniae cytoplasmic fumarate reductase on its modification by its own ApbE in recombinant Escherichia coli cells. The replacement of the flavin acceptor threonine with alanine completely abolished the modification reaction, whereas the replacements of conserved aspartate and serine had only minor effects. Effects of other substitutions, including replacing the acceptor threonine with serine, (a 10–55% decrease in the flavinylation degree) pinpointed important glycine and alanine residues and suggested an excessive capacity of the ApbE-based flavinylation system in vivo. Consistent with this deduction, drastic replacements of conserved leucine and threonine residues in the binding pocket that accommodates FMN residue still allowed appreciable flavinylation of the NqrC subunit of Vibrio harveyi Na+-translocating NADH:quinone oxidoreductase, despite a profound weakening of the isoalloxazine ring binding and an increase in its exposure to solvent.
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Affiliation(s)
- Yulia V Bertsova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Vorobievy Gory 1/40, Moscow 119234, Russia
| | - Marina V Serebryakova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Vorobievy Gory 1/40, Moscow 119234, Russia
| | - Victor A Anashkin
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Vorobievy Gory 1/40, Moscow 119234, Russia
| | - Alexander A Baykov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Vorobievy Gory 1/40, Moscow 119234, Russia
| | - Alexander V Bogachev
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Vorobievy Gory 1/40, Moscow 119234, Russia
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9
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Raba D, Yuan M, Fang X, Menzer WM, Xie B, Liang P, Tuz K, Minh DDL, Juárez O. Role of Subunit D in Ubiquinone-Binding Site of Vibrio cholerae NQR: Pocket Flexibility and Inhibitor Resistance. ACS OMEGA 2019; 4:19324-19331. [PMID: 31763556 PMCID: PMC6868883 DOI: 10.1021/acsomega.9b02707] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Accepted: 10/22/2019] [Indexed: 06/10/2023]
Abstract
The ion-pumping NADH: ubiquinone dehydrogenase (NQR) is a vital component of the respiratory chain of numerous species of marine and pathogenic bacteria, including Vibrio cholerae. This respiratory enzyme couples the transfer of electrons from NADH to ubiquinone (UQ) to the pumping of ions across the plasma membrane, producing a gradient that sustains multiple homeostatic processes. The binding site of UQ within the enzyme is an important functional and structural motif that could be used to design drugs against pathogenic bacteria. Our group recently located the UQ site in the interface between subunits B and D and identified the residues within subunit B that are important for UQ binding. In this study, we carried out alanine scanning mutagenesis of amino acid residues located in subunit D of V. cholerae NQR to understand their role in UQ binding and enzymatic catalysis. Moreover, molecular docking calculations were performed to characterize the structure of the site at the atomic level. The results show that mutations in these positions, in particular, in residues P185, L190, and F193, decrease the turnover rate and increase the Km for UQ. These mutants also showed an increase in the resistance against the inhibitor HQNO. The data indicate that residues in subunit D fulfill important structural roles, restricting and orienting UQ in a catalytically favorable position. In addition, mutations of these residues open the site and allow the simultaneous binding of substrate and inhibitors, producing partial inhibition, which appears to be a strategy used by Pseudomonas aeruginosa to avoid autopoisoning.
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Affiliation(s)
- Daniel
A. Raba
- Department
of Biological Sciences and Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616, United States
| | - Ming Yuan
- Department
of Biological Sciences and Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616, United States
| | - Xuan Fang
- Department
of Biological Sciences and Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616, United States
| | - William M. Menzer
- Department
of Biological Sciences and Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616, United States
| | - Bing Xie
- Department
of Biological Sciences and Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616, United States
| | - Pingdong Liang
- Department
of Biological Sciences and Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616, United States
| | - Karina Tuz
- Department
of Biological Sciences and Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616, United States
| | - David D. L. Minh
- Department
of Biological Sciences and Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616, United States
| | - Oscar Juárez
- Department
of Biological Sciences and Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616, United States
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10
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Fang X, Osipiuk J, Chakravarthy S, Yuan M, Menzer WM, Nissen D, Liang P, Raba DA, Tuz K, Howard AJ, Joachimiak A, Minh DDL, Juarez O. Conserved residue His-257 of Vibrio cholerae flavin transferase ApbE plays a critical role in substrate binding and catalysis. J Biol Chem 2019; 294:13800-13810. [PMID: 31350338 DOI: 10.1074/jbc.ra119.008261] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 07/23/2019] [Indexed: 12/22/2022] Open
Abstract
The flavin transferase ApbE plays essential roles in bacterial physiology, covalently incorporating FMN cofactors into numerous respiratory enzymes that use the integrated cofactors as electron carriers. In this work we performed a detailed kinetic and structural characterization of Vibrio cholerae WT ApbE and mutants of the conserved residue His-257, to understand its role in substrate binding and in the catalytic mechanism of this family. Bi-substrate kinetic experiments revealed that ApbE follows a random Bi Bi sequential kinetic mechanism, in which a ternary complex is formed, indicating that both substrates must be bound to the enzyme for the reaction to proceed. Steady-state kinetic analyses show that the turnover rates of His-257 mutants are significantly smaller than those of WT ApbE, and have increased Km values for both substrates, indicating that the His-257 residue plays important roles in catalysis and in enzyme-substrate complex formation. Analyses of the pH dependence of ApbE activity indicate that the pKa of the catalytic residue (pK ES1) increases by 2 pH units in the His-257 mutants, suggesting that this residue plays a role in substrate deprotonation. The crystal structures of WT ApbE and an H257G mutant were determined at 1.61 and 1.92 Å resolutions, revealing that His-257 is located in the catalytic site and that the substitution does not produce major conformational changes. We propose a reaction mechanism in which His-257 acts as a general base that deprotonates the acceptor residue, which subsequently performs a nucleophilic attack on FAD for flavin transfer.
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Affiliation(s)
- Xuan Fang
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois 60616
| | - Jerzy Osipiuk
- Center for Structural Genomics of Infectious Diseases (CSGID), Consortium for Advanced Science and Engineering, University of Chicago, Chicago, Illinois 60637.,Structural Biology Center, Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439
| | - Srinivas Chakravarthy
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois 60616.,Biophysics Collaborative Access Team, Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439
| | - Ming Yuan
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois 60616
| | - William M Menzer
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois 60616
| | - Devin Nissen
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois 60616
| | - Pingdong Liang
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois 60616
| | - Daniel A Raba
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois 60616
| | - Karina Tuz
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois 60616
| | - Andrew J Howard
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois 60616
| | - Andrzej Joachimiak
- Center for Structural Genomics of Infectious Diseases (CSGID), Consortium for Advanced Science and Engineering, University of Chicago, Chicago, Illinois 60637.,Structural Biology Center, Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439
| | - David D L Minh
- Department of Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616
| | - Oscar Juarez
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois 60616
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11
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Maynard A, Butler NL, Ito T, da Silva AJ, Murai M, Chen T, Koffas MAG, Miyoshi H, Barquera B. Antibiotic Korormicin A Kills Bacteria by Producing Reactive Oxygen Species. J Bacteriol 2019; 201:e00718-18. [PMID: 30858300 PMCID: PMC6509656 DOI: 10.1128/jb.00718-18] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Accepted: 03/07/2019] [Indexed: 11/20/2022] Open
Abstract
Korormicin is an antibiotic produced by some pseudoalteromonads which selectively kills Gram-negative bacteria that express the Na+-pumping NADH:quinone oxidoreductase (Na+-NQR.) We show that although korormicin is an inhibitor of Na+-NQR, the antibiotic action is not a direct result of inhibiting enzyme activity. Instead, perturbation of electron transfer inside the enzyme promotes a reaction between O2 and one or more redox cofactors in the enzyme (likely the flavin adenine dinucleotide [FAD] and 2Fe-2S center), leading to the production of reactive oxygen species (ROS). All Pseudoalteromonas contain the nqr operon in their genomes, including Pseudoalteromonas strain J010, which produces korormicin. We present activity data indicating that this strain expresses an active Na+-NQR and that this enzyme is not susceptible to korormicin inhibition. On the basis of our DNA sequence data, we show that the Na+-NQR of Pseudoalteromonas J010 carries an amino acid substitution (NqrB-G141A; Vibrio cholerae numbering) that in other Na+-NQRs confers resistance against korormicin. This is likely the reason that a functional Na+-NQR is able to exist in a bacterium that produces a compound that typically inhibits this enzyme and causes cell death. Korormicin is an effective antibiotic against such pathogens as Vibrio cholerae, Aliivibrio fischeri, and Pseudomonas aeruginosa but has no effect on Bacteroides fragilis and Bacteroides thetaiotaomicron, microorganisms that are important members of the human intestinal microflora.IMPORTANCE As multidrug antibiotic resistance in pathogenic bacteria continues to rise, there is a critical need for novel antimicrobial agents. An essential requirement for a useful antibiotic is that it selectively targets bacteria without significant effects on the eukaryotic hosts. Korormicin is an excellent candidate in this respect because it targets a unique respiratory enzyme found only in prokaryotes, the Na+-pumping NADH:quinone oxidoreductase (Na+-NQR). Korormicin is synthesized by some species of the marine bacterium Pseudoalteromonas and is a potent and specific inhibitor of Na+-NQR, an enzyme that is essential for the survival and proliferation of many Gram-negative human pathogens, including Vibrio cholerae and Pseudomonas aeruginosa, among others. Here, we identified how korormicin selectively kills these bacteria. The binding of korormicin to Na+-NQR promotes the formation of reactive oxygen species generated by the reaction of the FAD and the 2Fe-2S center cofactors with O2.
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Affiliation(s)
- Adam Maynard
- Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, New York, USA
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Nicole L Butler
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, New York, USA
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Takeshi Ito
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Adilson José da Silva
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York, USA
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York, USA
- Chemical Engineering Department, Federal University of Sao Carlos, Sao Paulo, Brazil
| | - Masatoshi Murai
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Tsute Chen
- The Forsyth Institute, Cambridge, Massachusetts, USA
- School of Dental Medicine, Harvard University, Boston, Massachusetts, USA
| | - Mattheos A G Koffas
- Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, New York, USA
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York, USA
- Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York, USA
| | - Hideto Miyoshi
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto, Japan
| | - Blanca Barquera
- Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, New York, USA
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York, USA
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12
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Occurrence and Function of the Na +-Translocating NADH:Quinone Oxidoreductase in Prevotella spp. Microorganisms 2019; 7:microorganisms7050117. [PMID: 31035603 PMCID: PMC6560451 DOI: 10.3390/microorganisms7050117] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Revised: 04/08/2019] [Accepted: 04/25/2019] [Indexed: 12/18/2022] Open
Abstract
Strictly anaerobic Prevotella spp. are characterized by their vast metabolic potential. As members of the Prevotellaceae family, they represent the most abundant organisms in the rumen and are typically found in monogastrics such as pigs and humans. Within their largely anoxic habitats, these bacteria are considered to rely primarily on fermentation for energy conservation. A recent study of the rumen microbiome identified multiple subunits of the Na+-translocating NADH:quinone oxidoreductase (NQR) belonging to different Prevotella spp. Commonly, the NQR is associated with biochemical energy generation by respiration. The existence of this Na+ pump in Prevotella spp. may indicate an important role for electrochemical Na+ gradients in their anaerobic metabolism. However, detailed information about the potential activity of the NQR in Prevotella spp. is not available. Here, the presence of a functioning NQR in the strictly anaerobic model organism P. bryantii B14 was verified by conducting mass spectrometric, biochemical, and kinetic experiments. Our findings propose that P. bryantii B14 and other Prevotella spp. retrieved from the rumen operate a respiratory NQR together with a fumarate reductase which suggests that these ruminal bacteria utilize a sodium motive force generated during respiratory NADH:fumarate oxidoreduction.
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13
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Flavin transferase: the maturation factor of flavin-containing oxidoreductases. Biochem Soc Trans 2018; 46:1161-1169. [PMID: 30154099 DOI: 10.1042/bst20180524] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 07/29/2018] [Accepted: 08/02/2018] [Indexed: 12/13/2022]
Abstract
Flavins, cofactors of many enzymes, are often covalently linked to these enzymes; for instance, flavin adenine mononucleotide (FMN) can form a covalent bond through either its phosphate or isoalloxazine group. The prevailing view had long been that all types of covalent attachment of flavins occur as autocatalytic reactions; however, in 2013, the first flavin transferase was identified, which catalyzes phosphoester bond formation between FMN and Na+-translocating NADH:quinone oxidoreductase in certain bacteria. Later studies have indicated that this post-translational modification is widespread in prokaryotes and is even found in some eukaryotes. Flavin transferase can occur as a separate ∼40 kDa protein or as a domain within the target protein and recognizes a degenerate DgxtsAT/S motif in various target proteins. The purpose of this review was to summarize the progress already achieved by studies of the structure, mechanism, and specificity of flavin transferase and to encourage future research on this topic. Interestingly, the flavin transferase gene (apbE) is found in many bacteria that have no known target protein, suggesting the presence of yet unknown flavinylation targets.
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14
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Catalytically important flavin linked through a phosphoester bond in a eukaryotic fumarate reductase. Biochimie 2018; 149:34-40. [DOI: 10.1016/j.biochi.2018.03.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Accepted: 03/28/2018] [Indexed: 02/03/2023]
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15
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Dibrov P, Dibrov E, Pierce GN. Na+-NQR (Na+-translocating NADH:ubiquinone oxidoreductase) as a novel target for antibiotics. FEMS Microbiol Rev 2017; 41:653-671. [PMID: 28961953 DOI: 10.1093/femsre/fux032] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 05/17/2017] [Indexed: 01/08/2023] Open
Abstract
The recent breakthrough in structural studies on Na+-translocating NADH:ubiquinone oxidoreductase (Na+-NQR) from the human pathogen Vibrio cholerae creates a perspective for the systematic design of inhibitors for this unique enzyme, which is the major Na+ pump in aerobic pathogens. Widespread distribution of Na+-NQR among pathogenic species, its key role in energy metabolism, its relation to virulence in different species as well as its absence in eukaryotic cells makes this enzyme especially attractive as a target for prospective antibiotics. In this review, the major biochemical, physiological and, especially, the pharmacological aspects of Na+-NQR are discussed to assess its 'target potential' for drug development. A comparison to other primary bacterial Na+ pumps supports the contention that NQR is a first rate prospective target for a new generation of antimicrobials. A new, narrowly targeted furanone inhibitor of NQR designed in our group is presented as a molecular platform for the development of anti-NQR remedies.
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Affiliation(s)
- Pavel Dibrov
- Department of Microbiology, University of Manitoba, Winnipeg, Canada
| | - Elena Dibrov
- Institute of Cardiovascular Sciences, Albrechtsen Research Centre, St. Boniface Hospital, Winnipeg, Canada.,Department of Physiology and Pathophysiology, Colleges of Medicine and Pharmacy, Faculty of Health Sciences, Winnipeg, Canada
| | - Grant N Pierce
- Institute of Cardiovascular Sciences, Albrechtsen Research Centre, St. Boniface Hospital, Winnipeg, Canada.,Department of Physiology and Pathophysiology, Colleges of Medicine and Pharmacy, Faculty of Health Sciences, Winnipeg, Canada
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16
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Fang X, Liang P, Raba DA, Rosas-Lemus M, Chakravarthy S, Tuz K, Juárez O. Kinetic characterization of Vibrio cholerae ApbE: Substrate specificity and regulatory mechanisms. PLoS One 2017; 12:e0186805. [PMID: 29065131 PMCID: PMC5655446 DOI: 10.1371/journal.pone.0186805] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 10/06/2017] [Indexed: 12/20/2022] Open
Abstract
ApbE is a member of a novel family of flavin transferases that incorporates flavin mononucleotide (FMN) to subunits of diverse respiratory complexes, which fulfill important homeostatic functions. In this work a detailed characterization of Vibrio cholerae ApbE physiologic activity, substrate specificity and pH dependency was carried out. The data obtained show novel characteristics of the regulation and function of this family. For instance, our experiments indicate that divalent cations are essential for ApbE function, and that the selectivity depends largely on size and the coordination sphere of the cation. Our data also show that ApbE regulation by pH, ADP and potassium is an important mechanism that enhances the adaptation, survival and colonization of V. cholerae in the small intestine. Moreover, studies of the pH-dependency of the activity show that the reaction is favored under alkaline conditions, with a pKa of 8.4. These studies, together with sequence and structure analysis allowed us to identify His257, which is absolutely conserved in the family, as a candidate for the residue whose deprotonation controls the activity. Remarkably, the mutant H257G abolished the flavin transfer activity, strongly indicating that this residue plays an important role in the catalytic mechanism of ApbE.
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Affiliation(s)
- Xuan Fang
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois, United States of America
| | - Pingdong Liang
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois, United States of America
| | - Daniel Alexander Raba
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois, United States of America
| | - Mónica Rosas-Lemus
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois, United States of America
| | - Srinivas Chakravarthy
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois, United States of America
- Biophysics Collaborative Access Team, Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois, United States of America
| | - Karina Tuz
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois, United States of America
| | - Oscar Juárez
- Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois, United States of America
- * E-mail:
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17
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Kang MG, Park J, Balboni G, Lim MH, Lee C, Rhee HW. Genetically Encodable Bacterial Flavin Transferase for Fluorogenic Protein Modification in Mammalian Cells. ACS Synth Biol 2017; 6:667-677. [PMID: 28035820 DOI: 10.1021/acssynbio.6b00284] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
A bacterial flavin transferase (ApbE) was recently employed for flavin mononucleotide (FMN) modification on the Na+-translocating NADH:quinone oxidoreductase C (NqrC) protein in the pathogenic Gram-negative bacterium Vibrio cholerae. We employed this unique post-translational modification in mammalian cells and found that the FMN transfer reaction robustly occurred when NqrC and ApbE were genetically targeted in the cytosol of live mammalian cells. Moreover, NqrC expression in the endoplasmic reticulum (NqrC-ER) induced the retro-translocation of NqrC to the cytosol, leading to the proteasome-mediated ER-associated degradation of NqrC, which is considered to be an innate immunological response toward the bacterial protein. This unexpected cellular process of NqrC-ER could be exploited for the construction of an in cellulo proteasome inhibitor screening system, and our proposed approach yielded substantially improved results compared to a previous method. In addition, a truncated version of RnfG (half-RnfG) was found to be potentially useful as a genetically encoded tag for monitoring protein-protein interactions in a specific compartment, even in the ER, in a live cell according to its fluorogenic post-translational modification via ApbE. This new genetically encoded system in mammalian cells should serve as a valuable tool for anticancer drug screening and other applications in molecular and synthetic biology.
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Affiliation(s)
| | | | - Gianfranco Balboni
- Department
of Life and Environmental Sciences, Pharmaceutical, Pharmacological
and Nutraceutical Sciences Unit, University of Cagliari, I-09124 Cagliari, Italy
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18
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Ito T, Murai M, Ninokura S, Kitazumi Y, Mezic KG, Cress BF, Koffas MAG, Morgan JE, Barquera B, Miyoshi H. Identification of the binding sites for ubiquinone and inhibitors in the Na +-pumping NADH-ubiquinone oxidoreductase from Vibrio cholerae by photoaffinity labeling. J Biol Chem 2017; 292:7727-7742. [PMID: 28298441 DOI: 10.1074/jbc.m117.781393] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Revised: 03/11/2017] [Indexed: 12/30/2022] Open
Abstract
The Na+-pumping NADH-quinone oxidoreductase (Na+-NQR) is the first enzyme of the respiratory chain and the main ion transporter in many marine and pathogenic bacteria, including Vibrio cholerae The V. cholerae Na+-NQR has been extensively studied, but its binding sites for ubiquinone and inhibitors remain controversial. Here, using a photoreactive ubiquinone PUQ-3 as well as two aurachin-type inhibitors [125I]PAD-1 and [125I]PAD-2 and photoaffinity labeling experiments on the isolated enzyme, we demonstrate that the ubiquinone ring binds to the NqrA subunit in the regions Leu-32-Met-39 and Phe-131-Lys-138, encompassing the rear wall of a predicted ubiquinone-binding cavity. The quinolone ring and alkyl side chain of aurachin bound to the NqrB subunit in the regions Arg-43-Lys-54 and Trp-23-Gly-89, respectively. These results indicate that the binding sites for ubiquinone and aurachin-type inhibitors are in close proximity but do not overlap one another. Unexpectedly, although the inhibitory effects of PAD-1 and PAD-2 were almost completely abolished by certain mutations in NqrB (i.e. G140A and E144C), the binding reactivities of [125I]PAD-1 and [125I]PAD-2 to the mutated enzymes were unchanged compared with those of the wild-type enzyme. We also found that photoaffinity labeling by [125I]PAD-1 and [125I]PAD-2, rather than being competitively suppressed in the presence of other inhibitors, is enhanced under some experimental conditions. To explain these apparently paradoxical results, we propose models for the catalytic reaction of Na+-NQR and its interactions with inhibitors on the basis of the biochemical and biophysical results reported here and in previous work.
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Affiliation(s)
- Takeshi Ito
- From the Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan and
| | - Masatoshi Murai
- From the Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan and
| | - Satoshi Ninokura
- From the Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan and
| | - Yuki Kitazumi
- From the Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan and
| | - Katherine G Mezic
- the Departments of Biological Sciences and.,Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180
| | - Brady F Cress
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180.,Chemical and Biological Engineering
| | - Mattheos A G Koffas
- the Departments of Biological Sciences and.,Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180.,Chemical and Biological Engineering
| | - Joel E Morgan
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180
| | - Blanca Barquera
- the Departments of Biological Sciences and.,Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180
| | - Hideto Miyoshi
- From the Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan and
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19
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Tuz K, Li C, Fang X, Raba DA, Liang P, Minh DDL, Juárez O. Identification of the Catalytic Ubiquinone-binding Site of Vibrio cholerae Sodium-dependent NADH Dehydrogenase: A NOVEL UBIQUINONE-BINDING MOTIF. J Biol Chem 2017; 292:3039-3048. [PMID: 28053088 DOI: 10.1074/jbc.m116.770982] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 12/29/2016] [Indexed: 11/06/2022] Open
Abstract
The sodium-dependent NADH dehydrogenase (Na+-NQR) is a key component of the respiratory chain of diverse prokaryotic species, including pathogenic bacteria. Na+-NQR uses the energy released by electron transfer between NADH and ubiquinone (UQ) to pump sodium, producing a gradient that sustains many essential homeostatic processes as well as virulence factor secretion and the elimination of drugs. The location of the UQ binding site has been controversial, with two main hypotheses that suggest that this site could be located in the cytosolic subunit A or in the membrane-bound subunit B. In this work, we performed alanine scanning mutagenesis of aromatic residues located in transmembrane helices II, IV, and V of subunit B, near glycine residues 140 and 141. These two critical glycine residues form part of the structures that regulate the site's accessibility. Our results indicate that the elimination of phenylalanine residue 211 or 213 abolishes the UQ-dependent activity, produces a leak of electrons to oxygen, and completely blocks the binding of UQ and the inhibitor HQNO. Molecular docking calculations predict that UQ interacts with phenylalanine 211 and pinpoints the location of the binding site in the interface of subunits B and D. The mutagenesis and structural analysis allow us to propose a novel UQ-binding motif, which is completely different compared with the sites of other respiratory photosynthetic complexes. These results are essential to understanding the electron transfer pathways and mechanism of Na+-NQR catalysis.
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Affiliation(s)
- Karina Tuz
- From the Departments of Biological Sciences and
| | - Chen Li
- Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616
| | - Xuan Fang
- From the Departments of Biological Sciences and
| | | | | | - David D L Minh
- Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616
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20
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Zhang L, Trncik C, Andrade SLA, Einsle O. The flavinyl transferase ApbE of Pseudomonas stutzeri matures the NosR protein required for nitrous oxide reduction. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1858:95-102. [PMID: 27864152 DOI: 10.1016/j.bbabio.2016.11.008] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 11/09/2016] [Accepted: 11/11/2016] [Indexed: 12/15/2022]
Abstract
The copper-containing enzyme nitrous oxide reductase (N2OR) catalyzes the transformation of nitrous oxide (N2O) to dinitrogen (N2) in microbial denitrification. Several accessory factors are essential for assembling the two copper sites CuA and CuZ, and for maintaining the activity. In particular, the deletion of either the transmembrane iron-sulfur flavoprotein NosR or the periplasmic protein NosX, a member of the ApbE family, abolishes N2O respiration. Here we demonstrate through biochemical and structural studies that the ApbE protein from Pseudomonas stutzeri, where the nosX gene is absent, is a monomeric FAD-binding protein that can serve as the flavin donor for NosR maturation via covalent flavinylation of a threonine residue. The flavin transfer reaction proceeds both in vivo and in vitro to generate post-translationally modified NosR with covalently bound FMN. Only FAD can act as substrate and the reaction requires a divalent cation, preferably Mg2+ that was also present in the crystal structure. In addition, the reaction is species-specific to a certain extent.
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Affiliation(s)
- Lin Zhang
- Institute for Biochemistry, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg im Breisgau, Germany
| | - Christian Trncik
- Institute for Biochemistry, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg im Breisgau, Germany
| | - Susana L A Andrade
- Institute for Biochemistry, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg im Breisgau, Germany; BIOSS Centre for Biological Signalling Studies, Schänzlestrasse 1, 79104 Freiburg im Breisgau, Germany
| | - Oliver Einsle
- Institute for Biochemistry, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg im Breisgau, Germany; BIOSS Centre for Biological Signalling Studies, Schänzlestrasse 1, 79104 Freiburg im Breisgau, Germany.
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21
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The Na+-Translocating NADH:Quinone Oxidoreductase Enhances Oxidative Stress in the Cytoplasm of Vibrio cholerae. J Bacteriol 2016; 198:2307-17. [PMID: 27325677 DOI: 10.1128/jb.00342-16] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 06/05/2016] [Indexed: 12/17/2022] Open
Abstract
UNLABELLED We searched for a source of reactive oxygen species (ROS) in the cytoplasm of the human pathogen Vibrio cholerae and addressed the mechanism of ROS formation using the dye 2',7'-dichlorofluorescein diacetate (DCFH-DA) in respiring cells. By comparing V. cholerae strains with or without active Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR), this respiratory sodium ion redox pump was identified as a producer of ROS in vivo The amount of cytoplasmic ROS detected in V. cholerae cells producing variants of Na(+)-NQR correlated well with rates of superoxide formation by the corresponding membrane fractions. Membranes from wild-type V. cholerae showed increased superoxide production activity (9.8 ± 0.6 μmol superoxide min(-1) mg(-1) membrane protein) compared to membranes from the mutant lacking Na(+)-NQR (0.18 ± 0.01 μmol min(-1) mg(-1)). Overexpression of plasmid-encoded Na(+)-NQR in the nqr deletion strain resulted in a drastic increase in the formation of superoxide (42.6 ± 2.8 μmol min(-1) mg(-1)). By analyzing a variant of Na(+)-NQR devoid of quinone reduction activity, we identified the reduced flavin adenine dinucleotide (FAD) cofactor of cytoplasmic NqrF subunit as the site for intracellular superoxide formation in V. cholerae The impact of superoxide formation by the Na(+)-NQR on the virulence of V. cholerae is discussed. IMPORTANCE In several studies, it was demonstrated that the Na(+)-NQR in V. cholerae affects virulence in a yet unknown manner. We identified the reduced FAD cofactor in the NADH-oxidizing NqrF subunit of the Na(+)-NQR as the site of superoxide formation in the cytoplasm of V. cholerae Our study provides the framework to understand how reactive oxygen species formed during respiration could participate in the regulated expression of virulence factors during the transition from aerobic to microaerophilic (intestinal) habitats. This hypothesis may turn out to be right for many other pathogens which, like V. cholerae, depend on the Na(+)-NQR as the sole electrogenic NADH dehydrogenase.
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22
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Tuz K, Mezic KG, Xu T, Barquera B, Juárez O. The Kinetic Reaction Mechanism of the Vibrio cholerae Sodium-dependent NADH Dehydrogenase. J Biol Chem 2015; 290:20009-21. [PMID: 26004776 DOI: 10.1074/jbc.m115.658773] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Indexed: 11/06/2022] Open
Abstract
The sodium-dependent NADH dehydrogenase (Na(+)-NQR) is the main ion transporter in Vibrio cholerae. Its activity is linked to the operation of the respiratory chain and is essential for the development of the pathogenic phenotype. Previous studies have described different aspects of the enzyme, including the electron transfer pathways, sodium pumping structures, cofactor and subunit composition, among others. However, the mechanism of the enzyme remains to be completely elucidated. In this work, we have studied the kinetic mechanism of Na(+)-NQR with the use of steady state kinetics and stopped flow analysis. Na(+)-NQR follows a hexa-uni ping-pong mechanism, in which NADH acts as the first substrate, reacts with the enzyme, and the oxidized NAD leaves the catalytic site. In this conformation, the enzyme is able to capture two sodium ions and transport them to the external side of the membrane. In the last step, ubiquinone is bound and reduced, and ubiquinol is released. Our data also demonstrate that the catalytic cycle involves two redox states, the three- and five-electron reduced forms. A model that gathers all available information is proposed to explain the kinetic mechanism of Na(+)-NQR. This model provides a background to understand the current structural and functional information.
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Affiliation(s)
- Karina Tuz
- From the Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois 60616 and
| | - Katherine G Mezic
- the Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, New York 12180
| | - Tianhao Xu
- From the Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois 60616 and
| | - Blanca Barquera
- the Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, New York 12180
| | - Oscar Juárez
- From the Department of Biological Sciences, Illinois Institute of Technology, Chicago, Illinois 60616 and
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23
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Hreha TN, Mezic KG, Herce HD, Duffy EB, Bourges A, Pryshchep S, Juarez O, Barquera B. Complete topology of the RNF complex from Vibrio cholerae. Biochemistry 2015; 54:2443-55. [PMID: 25831459 DOI: 10.1021/acs.biochem.5b00020] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
RNF is a redox-driven ion (Na(+) and in one case possibly H(+)) transporter present in many prokaryotes. It has been proposed that RNF performs a variety of reactions in different organisms, delivering low-potential reducing equivalents for specific cellular processes. RNF shares strong homology with the Na(+)-pumping respiratory enzyme Na(+)-NQR, although there are significant differences in subunit and redox cofactor composition. Here we report a topological analysis of the six subunits of RNF from Vibrio cholerae. Although individual subunits from other organisms have previously been studied, this is the first complete, experimentally derived, analysis of RNF from any one source. This has allowed us to identify and confirm key properties of RNF. The putative NADH binding site in RnfC is located on the cytoplasmic side of the membrane. FeS centers in RnfB and RnfC are also located on the cytoplasmic side. However, covalently attached FMNs in RnfD and RnfG are both located in the periplasm. RNF also contains a number of acidic residues that correspond to functionally important groups in Na(+)-NQR. The acidic residues involved in Na(+) uptake and many of those implicated in Na(+) translocation are topologically conserved. The topology of RNF closely matches the topology represented in the newly published structure of Na(+)-NQR, consistent with the close relation between the two enzymes. The topology of RNF is discussed in the context of the current structural model of Na(+)-NQR, and the proposed functionality of the RNF complex itself.
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24
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Borshchevskiy V, Round E, Bertsova Y, Polovinkin V, Gushchin I, Ishchenko A, Kovalev K, Mishin A, Kachalova G, Popov A, Bogachev A, Gordeliy V. Structural and functional investigation of flavin binding center of the NqrC subunit of sodium-translocating NADH:quinone oxidoreductase from Vibrio harveyi. PLoS One 2015; 10:e0118548. [PMID: 25734798 PMCID: PMC4348036 DOI: 10.1371/journal.pone.0118548] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Accepted: 01/17/2015] [Indexed: 12/20/2022] Open
Abstract
Na+-translocating NADH:quinone oxidoreductase (NQR) is a redox-driven sodium pump operating in the respiratory chain of various bacteria, including pathogenic species. The enzyme has a unique set of redox active prosthetic groups, which includes two covalently bound flavin mononucleotide (FMN) residues attached to threonine residues in subunits NqrB and NqrC. The reason of FMN covalent bonding in the subunits has not been established yet. In the current work, binding of free FMN to the apo-form of NqrC from Vibrio harveyi was studied showing very low affinity of NqrC to FMN in the absence of its covalent bonding. To study structural aspects of flavin binding in NqrC, its holo-form was crystallized and its 3D structure was solved at 1.56 Å resolution. It was found that the isoalloxazine moiety of the FMN residue is buried in a hydrophobic cavity and that its pyrimidine ring is squeezed between hydrophobic amino acid residues while its benzene ring is extended from the protein surroundings. This structure of the flavin-binding pocket appears to provide flexibility of the benzene ring, which can help the FMN residue to take the bended conformation and thus to stabilize the one-electron reduced form of the prosthetic group. These properties may also lead to relatively weak noncovalent binding of the flavin. This fact along with periplasmic location of the FMN-binding domains in the vast majority of NqrC-like proteins may explain the necessity of the covalent bonding of this prosthetic group to prevent its loss to the external medium.
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Affiliation(s)
- Valentin Borshchevskiy
- Moscow Institute of Physics and Technology, Dolgoprudniy, Russia
- Institute of Complex Systems (ICS-6) Structural Biochemistry, Research Centre Jülich GmbH, Jülich, Germany
| | - Ekaterina Round
- Institute of Complex Systems (ICS-6) Structural Biochemistry, Research Centre Jülich GmbH, Jülich, Germany
| | - Yulia Bertsova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Vitaly Polovinkin
- Moscow Institute of Physics and Technology, Dolgoprudniy, Russia
- Institute of Complex Systems (ICS-6) Structural Biochemistry, Research Centre Jülich GmbH, Jülich, Germany
| | - Ivan Gushchin
- Moscow Institute of Physics and Technology, Dolgoprudniy, Russia
- Institute of Complex Systems (ICS-6) Structural Biochemistry, Research Centre Jülich GmbH, Jülich, Germany
| | - Andrii Ishchenko
- Institute of Complex Systems (ICS-6) Structural Biochemistry, Research Centre Jülich GmbH, Jülich, Germany
| | - Kirill Kovalev
- Moscow Institute of Physics and Technology, Dolgoprudniy, Russia
| | - Alexey Mishin
- Moscow Institute of Physics and Technology, Dolgoprudniy, Russia
| | - Galina Kachalova
- A.N. Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow, Russia
| | | | - Alexander Bogachev
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
- * E-mail: (AB); (VG)
| | - Valentin Gordeliy
- Moscow Institute of Physics and Technology, Dolgoprudniy, Russia
- Institute of Complex Systems (ICS-6) Structural Biochemistry, Research Centre Jülich GmbH, Jülich, Germany
- Univ. Grenoble Alpes, IBS, Grenoble, France
- CNRS, IBS, Grenoble, France
- CEA, IBS, Grenoble, France
- * E-mail: (AB); (VG)
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Shea ME, Mezic KG, Juárez O, Barquera B. A mutation in Na(+)-NQR uncouples electron flow from Na(+) translocation in the presence of K(+). Biochemistry 2014; 54:490-6. [PMID: 25486106 DOI: 10.1021/bi501266e] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The sodium-pumping NADH:ubiquinone oxidoreductase (Na(+)-NQR) is a bacterial respiratory enzyme that obtains energy from the redox reaction between NADH and ubiquinone and uses this energy to create an electrochemical Na(+) gradient across the cell membrane. A number of acidic residues in transmembrane helices have been shown to be important for Na(+) translocation. One of these, Asp-397 in the NqrB subunit, is a key residue for Na(+) uptake and binding. In this study, we show that when this residue is replaced with asparagine, the enzyme acquires a new sensitivity to K(+); in the mutant, K(+) both activates the redox reaction and uncouples it from the ion translocation reaction. In the wild-type enzyme, Na(+) (or Li(+)) accelerates turnover while K(+) alone does not activate. In the NqrB-D397N mutant, K(+) accelerates the same internal electron transfer step (2Fe-2S → FMNC) that is accelerated by Na(+). This is the same step that is inhibited in mutants in which Na(+) uptake is blocked. NqrB-D397N is able to translocate Na(+) and Li(+), but when K(+) is introduced, no ion translocation is observed, regardless of whether Na(+) or Li(+) is present. Thus, this mutant, when it turns over in the presence of K(+), is the first, and currently the only, example of an uncoupled Na(+)-NQR. The fact the redox reaction and ion pumping become decoupled from each other only in the presence of K(+) provides a switch that promises to be a useful experimental tool.
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Affiliation(s)
- Michael E Shea
- Department of Biological Sciences and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute , Troy, New York 12180, United States
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26
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The sodium pumping NADH:quinone oxidoreductase (Na⁺-NQR), a unique redox-driven ion pump. J Bioenerg Biomembr 2014; 46:289-98. [PMID: 25052842 DOI: 10.1007/s10863-014-9565-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2014] [Accepted: 07/03/2014] [Indexed: 12/15/2022]
Abstract
The Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR) is a unique Na(+) pumping respiratory complex found only in prokaryotes, that plays a key role in the metabolism of marine and pathogenic bacteria, including Vibrio cholerae and other human pathogens. Na(+)-NQR is the main entrance for reducing equivalents into the respiratory chain of these bacteria, catalyzing the oxidation of NADH and the reduction of quinone, the free energy of this redox reaction drives the selective translocation of Na(+) across the cell membrane, which energizes key cellular processes. In this review we summarize the unique properties of Na(+)-NQR in terms of its redox cofactor composition, electron transfer reactions and a possible mechanism of coupling and pumping.
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Strickland M, Juárez O, Neehaul Y, Cook DA, Barquera B, Hellwig P. The conformational changes induced by ubiquinone binding in the Na+-pumping NADH:ubiquinone oxidoreductase (Na+-NQR) are kinetically controlled by conserved glycines 140 and 141 of the NqrB subunit. J Biol Chem 2014; 289:23723-33. [PMID: 25006248 DOI: 10.1074/jbc.m114.574640] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Na(+)-pumping NADH:ubiquinone oxidoreductase (Na(+)-NQR) is responsible for maintaining a sodium gradient across the inner bacterial membrane. This respiratory enzyme, which couples sodium pumping to the electron transfer between NADH and ubiquinone, is not present in eukaryotes and as such could be a target for antibiotics. In this paper it is shown that the site of ubiquinone reduction is conformationally coupled to the NqrB subunit, which also hosts the final cofactor in the electron transport chain, riboflavin. Previous work showed that mutations in conserved NqrB glycine residues 140 and 141 affect ubiquinone reduction and the proper functioning of the sodium pump. Surprisingly, these mutants did not affect the dissociation constant of ubiquinone or its analog HQNO (2-n-heptyl-4-hydroxyquinoline N-oxide) from Na(+)-NQR, which indicates that these residues do not participate directly in the ubiquinone binding site but probably control its accessibility. Indeed, redox-induced difference spectroscopy showed that these mutations prevented the conformational change involved in ubiquinone binding but did not modify the signals corresponding to bound ubiquinone. Moreover, data are presented that demonstrate the NqrA subunit is able to bind ubiquinone but with a low non-catalytically relevant affinity. It is also suggested that Na(+)-NQR contains a single catalytic ubiquinone binding site and a second site that can bind ubiquinone but is not active.
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Affiliation(s)
- Madeleine Strickland
- From the Laboratoire de Bioélectrochimie et Spectroscopie, UMR 7140, CNRS Université de Strasbourg, Strasbourg, France, 67000 and
| | - Oscar Juárez
- Department of Biological Sciences, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180
| | - Yashvin Neehaul
- From the Laboratoire de Bioélectrochimie et Spectroscopie, UMR 7140, CNRS Université de Strasbourg, Strasbourg, France, 67000 and
| | - Darcie A Cook
- Department of Biological Sciences, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180
| | - Blanca Barquera
- Department of Biological Sciences, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180
| | - Petra Hellwig
- From the Laboratoire de Bioélectrochimie et Spectroscopie, UMR 7140, CNRS Université de Strasbourg, Strasbourg, France, 67000 and
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Origin and evolution of the sodium -pumping NADH: ubiquinone oxidoreductase. PLoS One 2014; 9:e96696. [PMID: 24809444 PMCID: PMC4014512 DOI: 10.1371/journal.pone.0096696] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Accepted: 04/11/2014] [Indexed: 11/27/2022] Open
Abstract
The sodium -pumping NADH: ubiquinone oxidoreductase (Na+-NQR) is the main ion pump and the primary entry site for electrons into the respiratory chain of many different types of pathogenic bacteria. This enzymatic complex creates a transmembrane gradient of sodium that is used by the cell to sustain ionic homeostasis, nutrient transport, ATP synthesis, flagellum rotation and other essential processes. Comparative genomics data demonstrate that the nqr operon, which encodes all Na+-NQR subunits, is found in a large variety of bacterial lineages with different habitats and metabolic strategies. Here we studied the distribution, origin and evolution of this enzymatic complex. The molecular phylogenetic analyses and the organizations of the nqr operon indicate that Na+-NQR evolved within the Chlorobi/Bacteroidetes group, after the duplication and subsequent neofunctionalization of the operon that encodes the homolog RNF complex. Subsequently, the nqr operon dispersed through multiple horizontal transfer events to other bacterial lineages such as Chlamydiae, Planctomyces and α, β, γ and δ -proteobacteria. Considering the biochemical properties of the Na+-NQR complex and its physiological role in different bacteria, we propose a detailed scenario to explain the molecular mechanisms that gave rise to its novel redox- dependent sodium -pumping activity. Our model postulates that the evolution of the Na+-NQR complex involved a functional divergence from its RNF homolog, following the duplication of the rnf operon, the loss of the rnfB gene and the recruitment of the reductase subunit of an aromatic monooxygenase.
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Localization-controlled specificity of FAD:threonine flavin transferases in Klebsiella pneumoniae and its implications for the mechanism of Na(+)-translocating NADH:quinone oxidoreductase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1837:1122-9. [PMID: 24361839 DOI: 10.1016/j.bbabio.2013.12.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 12/04/2013] [Accepted: 12/13/2013] [Indexed: 12/22/2022]
Abstract
The Klebsiella pneumoniae genome contains genes for two putative flavin transferase enzymes (ApbE1 and ApbE2) that add FMN to protein Thr residues. ApbE1, but not ApbE2, has a periplasm-addressing signal sequence. The genome also contains genes for three target proteins with the Dxx(s/t)gAT flavinylation motif: two subunits of Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR), and a 99.5kDa protein, KPK_2907, with a previously unknown function. We show here that KPK_2907 is an active cytoplasmically-localized fumarate reductase. K. pneumoniae cells with an inactivated kpk_2907 gene lack cytoplasmic fumarate reductase activity, while retaining this activity in the membrane fraction. Complementation of the mutant strain with a kpk_2907-containing plasmid resulted in a complete recovery of cytoplasmic fumarate reductase activity. KPK_2907 produced in Escherichia coli cells contains 1mol/mol each of covalently bound FMN, noncovalently bound FMN and noncovalently bound FAD. Lesion in the ApbE1 gene in K. pneumoniae resulted in inactive Na(+)-NQR, but cytoplasmic fumarate reductase activity remained unchanged. On the contrary, lesion in the ApbE2 gene abolished the fumarate reductase but not the Na(+)-NQR activity. Both activities could be restored by transformation of the ApbE1- or ApbE2-deficient K. pneumoniae strains with plasmids containing the Vibrio cholerae apbE gene with or without the periplasm-directing signal sequence, respectively. Our data thus indicate that ApbE1 and ApbE2 bind FMN to Na(+)-NQR and fumarate reductase, respectively, and that, contrary to the presently accepted view, the FMN residues are on the periplasmic side of Na(+)-NQR. A new, "electron loop" mechanism is proposed for Na(+)-NQR, involving an electroneutral Na(+)/electron symport. This article is part of a Special Issue entitled: 18th European Bioenergetic Conference.
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Bertsova YV, Fadeeva MS, Kostyrko VA, Serebryakova MV, Baykov AA, Bogachev AV. Alternative pyrimidine biosynthesis protein ApbE is a flavin transferase catalyzing covalent attachment of FMN to a threonine residue in bacterial flavoproteins. J Biol Chem 2013; 288:14276-14286. [PMID: 23558683 DOI: 10.1074/jbc.m113.455402] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR) contains two flavin residues as redox-active prosthetic groups attached by a phosphoester bond to threonine residues in subunits NqrB and NqrC. We demonstrate here that flavinylation of truncated Vibrio harveyi NqrC at Thr-229 in Escherichia coli cells requires the presence of a co-expressed Vibrio apbE gene. The apbE genes cluster with genes for Na(+)-NQR and other FMN-binding flavoproteins in bacterial genomes and encode proteins with previously unknown function. Experiments with isolated NqrC and ApbE proteins confirmed that ApbE is the only protein factor required for NqrC flavinylation and also indicated that the reaction is Mg(2+)-dependent and proceeds with FAD but not FMN. Inactivation of the apbE gene in Klebsiella pneumoniae, wherein the nqr operon and apbE are well separated in the chromosome, resulted in a complete loss of the quinone reductase activity of Na(+)-NQR, consistent with its dependence on covalently bound flavin. Our data thus identify ApbE as a novel modifying enzyme, flavin transferase.
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Affiliation(s)
- Yulia V Bertsova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119992, Russia
| | - Maria S Fadeeva
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119992, Russia
| | - Vitaly A Kostyrko
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119992, Russia
| | - Marina V Serebryakova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119992, Russia
| | - Alexander A Baykov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119992, Russia
| | - Alexander V Bogachev
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119992, Russia.
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31
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Bogachev AV, Bertsova YV, Bloch DA, Verkhovsky MI. Urocanate reductase: identification of a novel anaerobic respiratory pathway in Shewanella oneidensis MR-1. Mol Microbiol 2012; 86:1452-63. [PMID: 23078170 DOI: 10.1111/mmi.12067] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/10/2012] [Indexed: 12/11/2022]
Abstract
Interpretation of the constantly expanding body of genomic information requires that the function of each gene be established. Here we report the genomic analysis and structural modelling of a previously uncharacterized redox-metabolism protein UrdA (SO_4620) of Shewanella oneidensis MR-1, which led to a discovery of the novel enzymatic activity, urocanate reductase. Further cloning and expression of urdA, as well as purification and biochemical study of the gene's product UrdA and redox titration of its prosthetic groups confirmed that the latter is indeed a flavin-containing enzyme catalysing the unidirectional reaction of two-electron reduction of urocanic acid to deamino-histidine, an activity not reported earlier. UrdA exhibits both high substrate affinity and high turnover rate (K(m) << 10 μM, k(cat) = 360 s(-1) ) and strong specificity in favour of urocanic acid. UrdA homologues are present in various bacterial genera, such as Shewanella, Fusobacterium and Clostridium, the latter including the human pathogen Clostridium tetani. The UrdA activity in S. oneidensis is induced by its substrate under anaerobic conditions and it enables anaerobic growth with urocanic acid as a sole terminal electron acceptor. The latter capability can provide the cells of UrdA-containing bacteria with a niche where no other bacteria can compete and survive.
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Affiliation(s)
- Alexander V Bogachev
- Department of Molecular Energetics of Microorganisms, A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119992, Russia.
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32
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Prokaryotic assembly factors for the attachment of flavin to complex II. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1827:637-47. [PMID: 22985599 DOI: 10.1016/j.bbabio.2012.09.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 09/05/2012] [Accepted: 09/07/2012] [Indexed: 01/01/2023]
Abstract
Complex II (also known as Succinate dehydrogenase or Succinate-ubiquinone oxidoreductase) is an important respiratory enzyme that participates in both the tricarboxylic acid cycle and electron transport chain. Complex II consists of four subunits including a catalytic flavoprotein (SdhA), an iron-sulphur subunit (SdhB) and two hydrophobic membrane anchors (SdhC and SdhD). Complex II also contains a number of redox cofactors including haem, Fe-S clusters and FAD, which mediate electron transfer from succinate oxidation to the reduction of the mobile electron carrier ubiquinone. The flavin cofactor FAD is an important redox cofactor found in many proteins that participate in oxidation/reduction reactions. FAD is predominantly bound non-covalently to flavoproteins, with only a small percentage of flavoproteins, such as complex II, binding FAD covalently. Aside from a few examples, the mechanisms of flavin attachment have been a relatively unexplored area. This review will discuss the FAD cofactor and the mechanisms used by flavoproteins to covalently bind FAD. Particular focus is placed on the attachment of FAD to complex II with an emphasis on SdhE (a DUF339/SDH5 protein previously termed YgfY), the first protein identified as an assembly factor for FAD attachment to flavoproteins in prokaryotes. The molecular details of SdhE-dependent flavinylation of complex II are discussed and comparisons are made to known cofactor chaperones. Furthermore, an evolutionary hypothesis is proposed to explain the distribution of SdhE homologues in bacterial and eukaryotic species. Mechanisms for regulating SdhE function and how this may be linked to complex II function in different bacterial species are also discussed. This article is part of a Special Issue entitled: Respiratory complex II: Role in cellular physiology and disease.
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Verkhovsky MI, Bogachev AV, Pivtsov AV, Bertsova YV, Fedin MV, Bloch DA, Kulik LV. Sodium-dependent movement of covalently bound FMN residue(s) in Na(+)-translocating NADH:quinone oxidoreductase. Biochemistry 2012; 51:5414-21. [PMID: 22697411 DOI: 10.1021/bi300322n] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR) is a component of respiratory electron-transport chain of various bacteria generating redox-driven transmembrane electrochemical Na(+) potential. We found that the change in Na(+) concentration in the reaction medium has no effect on the thermodynamic properties of prosthetic groups of Na(+)-NQR from Vibrio harveyi, as was revealed by the anaerobic equilibrium redox titration of the enzyme's EPR spectra. On the other hand, the change in Na(+) concentration strongly alters the EPR spectral properties of the radical pair formed by the two anionic semiquinones of FMN residues bound to the NqrB and NqrC subunits (FMN(NqrB) and FMN(NqrC)). Using data obtained by pulse X- and Q-band EPR as well as by pulse ENDOR and ELDOR spectroscopy, the interspin distance between FMN(NqrB) and FMN(NqrC) was found to be 15.3 Å in the absence and 20.4 Å in the presence of Na(+), respectively. Thus, the distance between the covalently bound FMN residues can vary by about 5 Å upon changes in Na(+) concentration. Using these results, we propose a scheme of the sodium potential generation by Na(+)-NQR based on the redox- and sodium-dependent conformational changes in the enzyme.
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Affiliation(s)
- Michael I Verkhovsky
- Department of Molecular Energetics of Microorganisms, A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Russia
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Juárez O, Neehaul Y, Turk E, Chahboun N, DeMicco JM, Hellwig P, Barquera B. The role of glycine residues 140 and 141 of subunit B in the functional ubiquinone binding site of the Na+-pumping NADH:quinone oxidoreductase from Vibrio cholerae. J Biol Chem 2012; 287:25678-85. [PMID: 22645140 DOI: 10.1074/jbc.m112.366088] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Na(+)-pumping NADH:quinone oxidoreductase (Na(+)-NQR) is the main entrance for electrons into the respiratory chain of many marine and pathogenic bacteria. The enzyme accepts electrons from NADH and donates them to ubiquinone, and the free energy released by this redox reaction is used to create an electrochemical gradient of sodium across the cell membrane. Here we report the role of glycine 140 and glycine 141 of the NqrB subunit in the functional binding of ubiquinone. Mutations at these residues altered the affinity of the enzyme for ubiquinol. Moreover, mutations in residue NqrB-G140 almost completely abolished the electron transfer to ubiquinone. Thus, NqrB-G140 and -G141 are critical for the binding and reaction of Na(+)-NQR with its electron acceptor, ubiquinone.
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Affiliation(s)
- Oscar Juárez
- Department of Biology, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
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35
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Neehaul Y, Juárez O, Barquera B, Hellwig P. Thermodynamic contribution to the regulation of electron transfer in the Na(+)-pumping NADH:quinone oxidoreductase from Vibrio cholerae. Biochemistry 2012; 51:4072-7. [PMID: 22533880 DOI: 10.1021/bi300343u] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Na(+)-pumping NADH:quinone oxidoreductase (Na(+)-NQR) is a fundamental enzyme of the oxidative phosphorylation metabolism and ionic homeostasis in several pathogenic and marine bacteria. To understand the mechanism that couples electron transfer with sodium translocation in Na(+)-NQR, the ion dependence of the redox potential of the individual cofactors was studied using a spectroelectrochemical approach. The redox potential of one of the FMN cofactors increased 90 mV in the presence of Na(+) or Li(+), compared to the redox potentials measured in the presence of other cations that are not transported by the enzyme, such as K(+), Rb(+), and NH(4)(+). This shift in redox potential of one FMN confirms the crucial role of the FMN anionic radicals in the Na(+) pumping mechanism and demonstrates that the control of the electron transfer rate has both kinetic (via conformational changes) and thermodynamic components.
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Affiliation(s)
- Yashvin Neehaul
- Laboratoire de spectroscopie vibrationnelle et electrochimie des biomolecules, Institut de Chimie, UMR 7177, Université de Strasbourg-CNRS, 67070 Strasbourg, France
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36
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Insights into the mechanism of electron transfer and sodium translocation of the Na(+)-pumping NADH:quinone oxidoreductase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:1823-32. [PMID: 22465856 DOI: 10.1016/j.bbabio.2012.03.017] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 03/13/2012] [Accepted: 03/15/2012] [Indexed: 11/22/2022]
Abstract
Na(+)-NQR is a unique energy-transducing complex, widely distributed among marine and pathogenic bacteria. It converts the energy from the oxidation of NADH and the reduction of quinone into an electrochemical Na(+)-gradient that can provide energy for the cell. Na(+)-NQR is not homologous to any other respiratory protein but is closely related to the RNF complex. In this review we propose that sodium pumping in Na(+)-NQR is coupled to the redox reactions by a novel mechanism, which operates at multiple sites, is indirect and mediated by conformational changes of the protein. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).
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Casutt MS, Schlosser A, Buckel W, Steuber J. The single NqrB and NqrC subunits in the Na(+)-translocating NADH: quinone oxidoreductase (Na(+)-NQR) from Vibrio cholerae each carry one covalently attached FMN. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:1817-22. [PMID: 22366169 DOI: 10.1016/j.bbabio.2012.02.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Revised: 02/03/2012] [Accepted: 02/09/2012] [Indexed: 12/19/2022]
Abstract
The Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR) is the prototype of a novel class of flavoproteins carrying a riboflavin phosphate bound to serine or threonine by a phosphodiester bond to the ribityl side chain. This membrane-bound, respiratory complex also contains one non-covalently bound FAD, one non-covalently bound riboflavin, ubiquinone-8 and a [2Fe-2S] cluster. Here, we report the quantitative analysis of the full set of flavin cofactors in the Na(+)-NQR and characterize the mode of linkage of the riboflavin phosphate to the membrane-bound NqrB and NqrC subunits. Release of the flavin by β-elimination and analysis of the cofactor demonstrates that the phosphate group is attached at the 5'-position of the ribityl as in authentic FMN and that the Na(+)-NQR contains approximately 1.7mol covalently bound FMN per mol non-covalently bound FAD. Therefore, each of the single NqrB and NqrC subunits in the Na(+)-NQR carries a single FMN. Elimination of the phosphodiester bond yields a dehydro-2-aminobutyrate residue, which is modified with β-mercaptoethanol by Michael addition. Proteolytic digestion followed by mass determination of peptide fragments reveals exclusive modification of threonine residues, which carry FMN in the native enzyme. The described reactions allow quantification and localization of the covalently attached FMNs in the Na(+)-NQR and in related proteins belonging to the Rhodobacter nitrogen fixation (RNF) family of enzymes. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).
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Affiliation(s)
- Marco S Casutt
- Department of Neuropathology, University of Freiburg, Freiburg, Germany.
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38
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Fadeeva MS, Bertsova YV, Euro L, Bogachev AV. Cys377 residue in NqrF subunit confers Ag(+) sensitivity of Na+-translocating NADH:quinone oxidoreductase from Vibrio harveyi. BIOCHEMISTRY (MOSCOW) 2011; 76:186-95. [PMID: 21568851 DOI: 10.1134/s0006297911020040] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR) is a component of the respiratory chain of various bacteria that generates a redox-driven transmembrane electrochemical Na(+) potential. The Na(+)-NQR activity is known to be specifically inhibited by low concentrations of silver ions. Replacement of the conserved Cys377 residue with alanine in the NqrF subunit of Na(+)-NQR from Vibrio harveyi resulted in resistance of the enzyme to Ag(+) and to other heavy metal ions. Analysis of the catalytic activity also showed that the rate of electron input into the mutant Na(+)-NQR decreased by about 14-fold in comparison to the wild type enzyme, whereas all other properties of (NqrF)C377A Na(+)-NQR including its stability remained unaffected.
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Affiliation(s)
- M S Fadeeva
- Department of Molecular Energetics of Microorganisms, Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Russia
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39
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Juárez O, Shea ME, Makhatadze GI, Barquera B. The role and specificity of the catalytic and regulatory cation-binding sites of the Na+-pumping NADH:quinone oxidoreductase from Vibrio cholerae. J Biol Chem 2011; 286:26383-90. [PMID: 21652714 DOI: 10.1074/jbc.m111.257873] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Na(+)-translocating NADH:quinone oxidoreductase is the entry site for electrons into the respiratory chain and the main sodium pump in Vibrio cholerae and many other pathogenic bacteria. In this work, we have employed steady-state and transient kinetics, together with equilibrium binding measurements to define the number of cation-binding sites and characterize their roles in the enzyme. Our results show that sodium and lithium ions stimulate enzyme activity, and that Na(+)-NQR enables pumping of Li(+), as well as Na(+) across the membrane. We also confirm that the enzyme is not able to translocate other monovalent cations, such as potassium or rubidium. Although potassium is not used as a substrate, Na(+)-NQR contains a regulatory site for this ion, which acts as a nonessential activator, increasing the activity and affinity for sodium. Rubidium can bind to the same site as potassium, but instead of being activated, enzyme turnover is inhibited. Activity measurements in the presence of both sodium and lithium indicate that the enzyme contains at least two functional sodium-binding sites. We also show that the binding sites are not exclusively responsible for ion selectivity, and other steps downstream in the mechanism also play a role. Finally, equilibrium-binding measurements with (22)Na(+) show that, in both its oxidized and reduced states, Na(+)-NQR binds three sodium ions, and that the affinity for sodium is the same for both of these states.
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Affiliation(s)
- Oscar Juárez
- Department of Biology and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
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Biegel E, Schmidt S, González JM, Müller V. Biochemistry, evolution and physiological function of the Rnf complex, a novel ion-motive electron transport complex in prokaryotes. Cell Mol Life Sci 2011; 68:613-34. [PMID: 21072677 PMCID: PMC11115008 DOI: 10.1007/s00018-010-0555-8] [Citation(s) in RCA: 248] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 09/30/2010] [Accepted: 10/01/2010] [Indexed: 11/25/2022]
Abstract
Microbes have a fascinating repertoire of bioenergetic enzymes and a huge variety of electron transport chains to cope with very different environmental conditions, such as different oxygen concentrations, different electron acceptors, pH and salinity. However, all these electron transport chains cover the redox span from NADH + H(+) as the most negative donor to oxygen/H(2)O as the most positive acceptor or increments thereof. The redox range more negative than -320 mV has been largely ignored. Here, we have summarized the recent data that unraveled a novel ion-motive electron transport chain, the Rnf complex, that energetically couples the cellular ferredoxin to the pyridine nucleotide pool. The energetics of the complex and its biochemistry, as well as its evolution and cellular function in different microbes, is discussed.
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Affiliation(s)
- Eva Biegel
- Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt/Main, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
| | - Silke Schmidt
- Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt/Main, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
| | - José M. González
- Department of Microbiology and Cell Biology, University of La Laguna, 38206 La Laguna, Tenerife Spain
| | - Volker Müller
- Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt/Main, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
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41
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Fadeeva MS, Bertsova YV, Verkhovsky MI, Bogachev AV. Site-directed mutagenesis of conserved cysteine residues in NqrD and NqrE subunits of Na+-translocating NADH:quinone oxidoreductase. BIOCHEMISTRY (MOSCOW) 2011; 73:123-9. [DOI: 10.1134/s0006297908020028] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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42
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Casutt MS, Huber T, Brunisholz R, Tao M, Fritz G, Steuber J. Localization and function of the membrane-bound riboflavin in the Na+-translocating NADH:quinone oxidoreductase (Na+-NQR) from Vibrio cholerae. J Biol Chem 2010; 285:27088-27099. [PMID: 20558724 PMCID: PMC2930708 DOI: 10.1074/jbc.m109.071126] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Revised: 06/16/2010] [Indexed: 12/29/2022] Open
Abstract
The sodium ion-translocating NADH:quinone oxidoreductase (Na(+)-NQR) from the human pathogen Vibrio cholerae is a respiratory membrane protein complex that couples the oxidation of NADH to the transport of Na(+) across the bacterial membrane. The Na(+)-NQR comprises the six subunits NqrABCDEF, but the stoichiometry and arrangement of these subunits are unknown. Redox-active cofactors are FAD and a 2Fe-2S cluster on NqrF, covalently attached FMNs on NqrB and NqrC, and riboflavin and ubiquinone-8 with unknown localization in the complex. By analyzing the cofactor content and NADH oxidation activity of subcomplexes of the Na(+)-NQR lacking individual subunits, the riboflavin cofactor was unequivocally assigned to the membrane-bound NqrB subunit. Quantitative analysis of the N-terminal amino acids of the holo-complex revealed that NqrB is present in a single copy in the holo-complex. It is concluded that the hydrophobic NqrB harbors one riboflavin in addition to its covalently attached FMN. The catalytic role of two flavins in subunit NqrB during the reduction of ubiquinone to ubiquinol by the Na(+)-NQR is discussed.
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Affiliation(s)
- Marco S Casutt
- Department of Neuropathology, Breisacherstrasse 64, University of Freiburg, 79106 Freiburg, Germany
| | - Tamara Huber
- Department of Biochemistry, University of Zurich, 8057 Zurich, Switzerland
| | - René Brunisholz
- Functional Genomics Centre Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Minli Tao
- Department of Biochemistry, University of Zurich, 8057 Zurich, Switzerland
| | - Günter Fritz
- Department of Neuropathology, Breisacherstrasse 64, University of Freiburg, 79106 Freiburg, Germany
| | - Julia Steuber
- Department of Biochemistry, University of Zurich, 8057 Zurich, Switzerland.
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43
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Energy transducing redox steps of the Na+-pumping NADH:quinone oxidoreductase from Vibrio cholerae. Proc Natl Acad Sci U S A 2010; 107:12505-10. [PMID: 20616050 DOI: 10.1073/pnas.1002866107] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Na(+)-NQR is a unique respiratory enzyme that couples the free energy of electron transfer reactions to electrogenic pumping of sodium across the cell membrane. This enzyme is found in many marine and pathogenic bacteria where it plays an analogous role to the H(+)-pumping complex I. It has generally been assumed that the sodium pump of Na(+)-NQR operates on the basis of thermodynamic coupling between reduction of a single redox cofactor and the binding of sodium at a nearby site. In this study, we have defined the coupling to sodium translocation of individual steps in the redox reaction of Na(+)-NQR. Sodium uptake takes place in the reaction step in which an electron moves from the 2Fe-2S center to FMN(C), while the translocation of sodium across the membrane dielectric (and probably its release into the external medium) occurs when an electron moves from FMN(B) to riboflavin. This argues against a single-site coupling model because the redox steps that drive these two parts of the sodium pumping process do not have any redox cofactor in common. The significance of these results for the mechanism of coupling is discussed, and we proposed that Na(+)-NQR operates through a novel mechanism based on kinetic coupling, mediated by conformational changes.
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44
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Marcia M, Ermler U, Peng G, Michel H. A new structure-based classification of sulfide:quinone oxidoreductases. Proteins 2010; 78:1073-83. [PMID: 20077566 DOI: 10.1002/prot.22665] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Sulfide:quinone oxidoreductases (SQR) are ubiquitous membrane-bound flavoproteins involved in sulfide detoxification, in sulfide-dependent energy conservation processes and potenatially in the homeostasis of the neurotransmitter sulfide. The first 2 structures of SQRs from the bacterium Aquifex aeolicus (Marcia et al., Proc Natl Acad Sci USA 2009; 106:9625-9630) and the archaeon Acidianus ambivalens (Brito et al., Biochemistry 2009; 48:5613-5622) were determined recently by X-ray crystallography revealing unexpected differences in the active sites and in flavin adenine dinucleotide binding. Besides the reciprocal differences, they show a different conformation of the active site compared with another sulfide oxidizing enzyme, the flavocytochrome c:sulfide dehydrogenase (FCSD) from Allochromatium vinosum (protein data bank id: 1FCD). In addition to the new structural data, the number of available SQR-like protein sequences is continuously increasing (Pham et al., Microbiology 2008; 154:3112-3121) and the SQR activity of new members of this protein family was recently proven too (Chan et al., J Bacteriol 2009; 191:1026-1034). In the light of the new data, here we revisit the previously proposed contradictory SQR classification and we define new structure-based sequence fingerprints that support a subdivision of the SQR family into six groups. Our report summarizes the state-of-art knowledge about SQRs and highlights the questions that still remain unanswered. Despite two decades of work already done on these enzymes, new and most exciting discoveries can be expected in the future.
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Affiliation(s)
- Marco Marcia
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, 60596 Frankfurt am Main, Germany
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45
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Oppenheimer M, Pierce BS, Crawford JA, Ray K, Helm RF, Sobrado P. Recombinant expression, purification, and characterization of ThmD, the oxidoreductase component of tetrahydrofuran monooxygenase. Arch Biochem Biophys 2010; 496:123-31. [PMID: 20159007 DOI: 10.1016/j.abb.2010.02.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Revised: 02/09/2010] [Accepted: 02/10/2010] [Indexed: 11/29/2022]
Abstract
Tetrahydrofuran monooxygenase (Thm) catalyzes the NADH-and oxygen-dependent hydroxylation of tetrahydrofuran to 2-hydroxytetrahydrofuran. Thm is composed of a hydroxylase enzyme, a regulatory subunit, and an oxidoreductase named ThmD. ThmD was expressed in Escherichia coli as a fusion to maltose-binding protein (MBP) and isolated to homogeneity after removal of the MBP. Purified ThmD contains covalently bound FAD, [2Fe-2S] center, and was shown to use ferricyanide, cytochrome c, 2,6-dichloroindophenol, and to a lesser extent, oxygen as surrogate electron acceptors. ThmD displays 160-fold preference for NADH over NADPH and functions as a monomer. The flavin-binding domain of ThmD (ThmD-FD) was purified and characterized. ThmD-FD displayed similar activity as the full-length ThmD and showed a unique flavin spectrum with a major peak at 463nm and a small peak at 396 nm. Computational modeling and mutagenesis analyses suggest a novel three-dimensional fold or covalent flavin attachment in ThmD.
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46
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Sodium-translocating NADH:quinone oxidoreductase as a redox-driven ion pump. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:738-46. [PMID: 20056102 DOI: 10.1016/j.bbabio.2009.12.020] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2009] [Revised: 12/17/2009] [Accepted: 12/24/2009] [Indexed: 11/20/2022]
Abstract
The Na+-translocating NADH:ubiquinone oxidoreductase (Na+-NQR) is a component of the respiratory chain of various bacteria. This enzyme is an analogous but not homologous counterpart of mitochondrial Complex I. Na+-NQR drives the same chemistry and also uses released energy to translocate ions across the membrane, but it pumps Na+ instead of H+. Most likely the mechanism of sodium pumping is quite different from that of proton pumping (for example, it could not accommodate the Grotthuss mechanism of ion movement); this is why the enzyme structure, subunits and prosthetic groups are completely special. This review summarizes modern knowledge on the structural and catalytic properties of bacterial Na+-translocating NADH:quinone oxidoreductases. The sequence of electron transfer through the enzyme cofactors and thermodynamic properties of those cofactors is discussed. The resolution of the intermediates of the catalytic cycle and localization of sodium-dependent steps are combined in a possible molecular mechanism of sodium transfer by the enzyme.
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47
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Juárez O, Athearn K, Gillespie P, Barquera B. Acid residues in the transmembrane helices of the Na+-pumping NADH:quinone oxidoreductase from Vibrio cholerae involved in sodium translocation. Biochemistry 2009; 48:9516-24. [PMID: 19694431 DOI: 10.1021/bi900845y] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Vibrio cholerae and many other marine and pathogenic bacteria possess a unique respiratory complex, the Na(+)-pumping NADH:quinone oxidoreductase (Na(+)-NQR), which pumps Na(+) across the cell membrane using the energy released by the redox reaction between NADH and ubiquinone. To function as a selective sodium pump, Na(+)-NQR must contain structures that (1) allow the sodium ion to pass through the hydrophobic core of the membrane and (2) provide cation specificity to the translocation system. In other sodium-transporting proteins, the structures that carry out these roles frequently include aspartate and glutamate residues. The negative charge of these residues facilitates binding and translocation of sodium. In this study, we have analyzed mutants of acid residues located in the transmembrane helices of subunits B, D, and E of Na(+)-NQR. The results are consistent with the participation of seven of these residues in the translocation process of sodium. Mutations at NqrB-D397, NqrD-D133, and NqrE-E95 produced a decrease of approximately >or=10-fold in the apparent affinity of the enzyme for sodium (Km(app)(Na+)), which suggests that these residues may form part of a sodium-binding site. Mutation at other residues, including NqrB-E28, NqrB-E144, NqrB-E346, and NqrD-D88, had a strong effect on the quinone reductase activity of the enzyme and its sodium sensitivity, but a weaker effect on the apparent sodium affinity, consistent with a possible role in sodium conductance pathways.
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Affiliation(s)
- Oscar Juárez
- Department of Biology and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
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48
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Bogachev AV, Kulik LV, Bloch DA, Bertsova YV, Fadeeva MS, Verkhovsky MI. Redox properties of the prosthetic groups of Na(+)-translocating nadh:quinone oxidoreductase. 1. Electron paramagnetic resonance study of the enzyme. Biochemistry 2009; 48:6291-8. [PMID: 19496621 DOI: 10.1021/bi900524m] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Redox properties of all EPR-detectable prosthetic groups of Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR) from Vibrio harveyi were studied at pH 7.5 using cryo-EPR spectroelectrochemistry. Titration shows five redox transitions. One with E(m) = -275 mV belongs to the reduction of the [2Fe-2S] cluster, and the four others reflect redox transitions of flavin cofactors. Two transitions (E(m)(1) = -190 mV and E(m)(2) = -275 mV) originate from the formation of FMN anion radical, covalently bound to the NqrC subunit, and its subsequent reduction. The remaining two transitions arise from the two other flavin cofactors. A high potential (E(m) = -10 mV) transition corresponds to the reduction of riboflavin neutral radical, which is stable at rather high redox potentials. An E(m) = -130 mV transition reflects the formation of FMN anion radical from a flavin covalently bound to the NqrB subunit, which stays as a radical down to very low potentials. Taking into account the EPR-silent, two-electron transition of noncovalently bound FAD located in the NqrF subunit, there are four flavins in Na(+)-NQR all together. Defined by dipole-dipole magnetic interaction measurements, the interspin distance between the [2Fe-2S](+) cluster and the NqrB subunit-bound FMN anion radical is found to be 22.5 +/- 1.5 A, which means that for the functional electron transfer between these two centers another cofactor, most likely FMN bound to the NqrC subunit, should be located.
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Affiliation(s)
- Alexander V Bogachev
- Department of Molecular Energetics of Microorganisms, A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119992, Russia
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49
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Bogachev AV, Bloch DA, Bertsova YV, Verkhovsky MI. Redox properties of the prosthetic groups of Na(+)-translocating NADH:quinone oxidoreductase. 2. Study of the enzyme by optical spectroscopy. Biochemistry 2009; 48:6299-304. [PMID: 19496622 DOI: 10.1021/bi900525v] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Redox titration of the electronic spectra of the prosthetic groups of the Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR) from Vibrio harveyi at different pH values showed five redox transitions corresponding to the four flavin cofactors of the enzyme and one additional transition reflecting oxidoreduction of the [2Fe-2S] cluster. The pH dependence of the measured midpoint redox potentials showed that the two-electron reduction of the FAD located in the NqrF subunit was coupled with the uptake of only one H(+). The one-electron reduction of neutral semiquinone of riboflavin and the formation of anion flavosemiquinone from the oxidized FMN bound to the NqrB subunit were not coupled to any proton uptake. The two sequential one-electron reductions of the FMN residue bound to the NqrC subunit showed pH-independent formation of anion radical in the first step and the formation of fully reduced flavin coupled to the uptake of one H(+) in the second step. All four flavins stayed in the anionic form in the fully reduced enzyme. None of the six redox transitions in Na(+)-NQR showed dependence of its midpoint redox potential on the concentration of sodium ions. A model of the sequence of electron transfer steps in the enzyme is suggested.
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Affiliation(s)
- Alexander V Bogachev
- Department of Molecular Energetics of Microorganisms, A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119992, Russia
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50
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Heuts DPHM, Scrutton NS, McIntire WS, Fraaije MW. What's in a covalent bond? On the role and formation of covalently bound flavin cofactors. FEBS J 2009; 276:3405-27. [PMID: 19438712 DOI: 10.1111/j.1742-4658.2009.07053.x] [Citation(s) in RCA: 140] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Many enzymes use one or more cofactors, such as biotin, heme, or flavin. These cofactors may be bound to the enzyme in a noncovalent or covalent manner. Although most flavoproteins contain a noncovalently bound flavin cofactor (FMN or FAD), a large number have these cofactors covalently linked to the polypeptide chain. Most covalent flavin-protein linkages involve a single cofactor attachment via a histidyl, tyrosyl, cysteinyl or threonyl linkage. However, some flavoproteins contain a flavin that is tethered to two amino acids. In the last decade, many studies have focused on elucidating the mechanism(s) of covalent flavin incorporation (flavinylation) and the possible role(s) of covalent protein-flavin bonds. These endeavors have revealed that covalent flavinylation is a post-translational and self-catalytic process. This review presents an overview of the known types of covalent flavin bonds and the proposed mechanisms and roles of covalent flavinylation.
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Affiliation(s)
- Dominic P H M Heuts
- Laboratory of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, The Netherlands
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