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Steuber J, Fritz G. The Na +-translocating NADH:quinone oxidoreductase (Na +-NQR): Physiological role, structure and function of a redox-driven, molecular machine. BIOCHIMICA ET BIOPHYSICA ACTA. BIOENERGETICS 2024; 1865:149485. [PMID: 38955304 DOI: 10.1016/j.bbabio.2024.149485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2024] [Accepted: 06/27/2024] [Indexed: 07/04/2024]
Abstract
Many bacterial processes are powered by the sodium motive force (smf) and in case of pathogens, the smf contributes to virulence. Vibrio cholerae, the causative agent of Cholera disease, possesses a Na+-translocating NADH:quinone oxidoreductase (NQR), a six-subunit membrane protein assembly. The 3D structure of NQR revealed the arrangement of the six subunits NqrABCDEF, the position of all redox cofactors (four flavins, two [2Fe-2S] centers) and the binding sites for the substrates NADH (in NqrF) and ubiquinone (in NqrB). Upon oxidation of NADH, electrons are shuttled twice across the membrane, starting with cytoplasmic FADNqrF and electron transfer to the [2Fe2S] clusterNqrF and from there to an intra-membranous [2Fe-2S] clusterNqrDE, periplasmic FMNNqrC, FMNNqrB and from there to riboflavinNqrB. This riboflavin is located at the cytoplasmic entry site of the sodium channel in NqrB, and it donates electrons to ubiquinone-8 positioned at the cytoplasmic side of NqrB. Targeting the substrate binding sites of NQR is a promising strategy to identify new inhibitors against many bacterial pathogens. Detailed structural information on the binding mode of natural inhibitors and small molecules in the active sites of NQR is now available, paving the way for the development of new antibiotics. The NQR shows different conformations as revealed in recent cryo-EM and crystallographic studies combined with spectroscopic analyses. These conformations represent distinct steps in the catalytic cycle. Considering the structural and functional data available, we propose a mechanism of Na+-NQR based on conformational coupling of electron transfer and Na+ translocation reaction steps.
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Affiliation(s)
- Julia Steuber
- Institute of Biology, Department of Cellular Microbiology, University of Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany.
| | - Günter Fritz
- Institute of Biology, Department of Cellular Microbiology, University of Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany.
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2
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Zheng Y, Yan W, Dou C, Zhou D, Chen Y, Jin Y, Yang L, Zeng X, Cheng W. Structural insights into the catalytic and inhibitory mechanisms of the flavin transferase FmnB in Listeria monocytogenes. MedComm (Beijing) 2022; 3:e99. [PMID: 35281791 PMCID: PMC8906456 DOI: 10.1002/mco2.99] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2021] [Revised: 10/05/2021] [Accepted: 10/20/2021] [Indexed: 02/05/2023] Open
Abstract
Listeria monocytogenes, a food-borne Gram-positive pathogen, often causes diseases such as gastroenteritis, bacterial sepsis, and meningitis. Newly discovered extracellular electron transfer (EET) from L. monocytogenes plays critical roles in the generation of redox molecules as electron carriers in bacteria. A Mg2+-dependent protein flavin mononucleotide (FMN) transferase (FmnB; UniProt: LMRG_02181) in EET is responsible for the transfer of electrons from intracellular to extracellular by hydrolyzing cofactor flavin adenine dinucleotide (FAD) and transferring FMN. FmnB homologs have been investigated in Gram-negative bacteria but have been less well studied in Gram-positive bacteria. In particular, the catalytic and inhibitory mechanisms of FmnB homologs remain elusive. Here, we report a series of crystal structures of apo-FmnB and FmnB complexed with substrate FAD, three inhibitors AMP, ADP, and ATP, revealing the unusual catalytic triad center (Asp301-Ser257-His273) of FmnB. The three inhibitors indeed inhibited the activity of FmnB in varying degrees by occupying the binding site of the FAD substrate. The key residue Arg262 of FmnB was profoundly affected by ADP but not AMP or ATP. Overall, our studies not only provide insights into the promiscuous ligand recognition behavior of FmnB but also shed light on its catalytic and inhibitory mechanisms.
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Affiliation(s)
- Yanhui Zheng
- Division of Respiratory and Critical Care MedicineRespiratory Infection and Intervention Laboratory of Frontiers Science Center for Disease‐Related Molecular NetworkState Key Laboratory of BiotherapyWest China Hospital of Sichuan UniversityChengduChina
| | - Weizhu Yan
- Division of Respiratory and Critical Care MedicineRespiratory Infection and Intervention Laboratory of Frontiers Science Center for Disease‐Related Molecular NetworkState Key Laboratory of BiotherapyWest China Hospital of Sichuan UniversityChengduChina
| | - Chao Dou
- Division of Respiratory and Critical Care MedicineRespiratory Infection and Intervention Laboratory of Frontiers Science Center for Disease‐Related Molecular NetworkState Key Laboratory of BiotherapyWest China Hospital of Sichuan UniversityChengduChina
| | - Dan Zhou
- Division of Respiratory and Critical Care MedicineRespiratory Infection and Intervention Laboratory of Frontiers Science Center for Disease‐Related Molecular NetworkState Key Laboratory of BiotherapyWest China Hospital of Sichuan UniversityChengduChina
| | - Yunying Chen
- Division of Respiratory and Critical Care MedicineRespiratory Infection and Intervention Laboratory of Frontiers Science Center for Disease‐Related Molecular NetworkState Key Laboratory of BiotherapyWest China Hospital of Sichuan UniversityChengduChina
| | - Ying Jin
- Division of Respiratory and Critical Care MedicineRespiratory Infection and Intervention Laboratory of Frontiers Science Center for Disease‐Related Molecular NetworkState Key Laboratory of BiotherapyWest China Hospital of Sichuan UniversityChengduChina
| | - Lulu Yang
- Division of Respiratory and Critical Care MedicineRespiratory Infection and Intervention Laboratory of Frontiers Science Center for Disease‐Related Molecular NetworkState Key Laboratory of BiotherapyWest China Hospital of Sichuan UniversityChengduChina
| | - Xiaotao Zeng
- Division of Respiratory and Critical Care MedicineRespiratory Infection and Intervention Laboratory of Frontiers Science Center for Disease‐Related Molecular NetworkState Key Laboratory of BiotherapyWest China Hospital of Sichuan UniversityChengduChina
| | - Wei Cheng
- Division of Respiratory and Critical Care MedicineRespiratory Infection and Intervention Laboratory of Frontiers Science Center for Disease‐Related Molecular NetworkState Key Laboratory of BiotherapyWest China Hospital of Sichuan UniversityChengduChina
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3
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Tong Y, Lee M, Drenth J, Fraaije MW. Flavin-tag: A Facile Method for Site-Specific Labeling of Proteins with a Flavin Fluorophore. Bioconjug Chem 2021; 32:1559-1563. [PMID: 34304568 DOI: 10.1021/acs.bioconjchem.1c00306] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Site-specific protein labeling methods are highly valuable tools for research and applications. We present a new protein labeling method that allows covalent attachment of a chromo- and fluorogenic flavin (FMN) to any targeted protein using a short flavinylation peptide-tag. We show that this peptide can be as short as 7 residues and can be located at the N-terminus, C-terminus, or in internal regions of the target protein. Analogous to kinase-catalyzed phosphorylation, the flavin is covalently attached via a stable phosphothreonyl linkage. The site-specific covalent tethering of FMN is accomplished by using a bacterial flavin transferase. The covalent coupling of FMN was shown to work in Escherichia coli and Saccharomyces cerevisiae cells and could be performed in vitro, rendering the "Flavin-tag" method a powerful tool for the selective decoration of proteins with a biocompatible redox-active fluorescent chromophore.
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Affiliation(s)
- Yapei Tong
- Molecular Enzymology Group, University of Groningen, Nijenborgh 4, Groningen 9747AG, The Netherlands
| | - Misun Lee
- Molecular Enzymology Group, University of Groningen, Nijenborgh 4, Groningen 9747AG, The Netherlands
| | - Jeroen Drenth
- Molecular Enzymology Group, University of Groningen, Nijenborgh 4, Groningen 9747AG, The Netherlands
| | - Marco W Fraaije
- Molecular Enzymology Group, University of Groningen, Nijenborgh 4, Groningen 9747AG, The Netherlands
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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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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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6
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Kim D, Na EJ, Kim S, Kim JS, Jung YH, Cao J, Han HJ, Bang IS, Yoo JW, Ha NC, Choi SH. Transcriptomic Identification and Biochemical Characterization of HmpA, a Nitric Oxide Dioxygenase, Essential for Pathogenesis of Vibrio vulnificus. Front Microbiol 2019; 10:2208. [PMID: 31616401 PMCID: PMC6768983 DOI: 10.3389/fmicb.2019.02208] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Accepted: 09/09/2019] [Indexed: 12/29/2022] Open
Abstract
Nitric oxide (NO) and its derivatives are important effectors of host innate immunity, disrupting cellular function of infecting pathogens. Transcriptome analysis of Vibrio vulnificus, an opportunistic human pathogen, identified a set of genes induced upon exposure to NO. Among them, VvhmpA (V. vulnificus hmpA), encoding a multidomain NO dioxygenase, was the most greatly induced upon exposure to NO and was thus further characterized. Absorption spectra demonstrated that VvHmpA is a heme protein in which the heme iron can exist in either reduced, NO-bound, or oxidized state. Biochemical studies revealed that VvHmpA is a flavohemoglobin containing equimolar amounts of heme and FAD as cofactors. The KM and kcat values of VvHmpA for NO at 37°C, the temperature encountered by V. vulnificus in the host, were greater than those at 30°C, indicating that VvHmpA detoxifies high levels of NO effectively during infection. Compared with the wild type, the VvhmpA mutant exhibited a lower NO-decomposition activity and impaired growth in the presence of NO in vitro. Also, the cytotoxicity and survival of the VvhmpA mutant infecting the NO-producing murine macrophage cells were lower than those of the wild type. Furthermore, the mouse lethality of the VvhmpA mutant was reduced compared to that of the parental wild type. The combined results revealed that VvHmpA is a potent virulence factor that is induced upon exposure to NO and important for the survival and pathogenesis of V. vulnificus during infection.
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Affiliation(s)
- Dukyun Kim
- National Research Laboratory of Molecular Microbiology and Toxicology, Seoul National University, Seoul, South Korea.,Department of Agricultural Biotechnology, and Center for Food Safety and Toxicology, Seoul National University, Seoul, South Korea
| | - Eun Jung Na
- National Research Laboratory of Molecular Microbiology and Toxicology, Seoul National University, Seoul, South Korea.,Department of Agricultural Biotechnology, and Center for Food Safety and Toxicology, Seoul National University, Seoul, South Korea
| | - Suhyeon Kim
- Department of Agricultural Biotechnology, and Center for Food Safety and Toxicology, Seoul National University, Seoul, South Korea
| | - Jung Sung Kim
- Department of Microbiology and Immunology, Chosun University School of Dentistry, Gwangju, South Korea
| | - Young Hyun Jung
- Department of Veterinary Physiology, College of Veterinary Medicine, Research Institute for Veterinary Medicine, BK21 PLUS Creative Veterinary Research Center, Seoul National University, Seoul, South Korea
| | - Jiafu Cao
- College of Pharmacy, Pusan National University, Busan, South Korea
| | - Ho Jae Han
- Department of Veterinary Physiology, College of Veterinary Medicine, Research Institute for Veterinary Medicine, BK21 PLUS Creative Veterinary Research Center, Seoul National University, Seoul, South Korea
| | - Iel Soo Bang
- Department of Microbiology and Immunology, Chosun University School of Dentistry, Gwangju, South Korea
| | - Jin-Wook Yoo
- College of Pharmacy, Pusan National University, Busan, South Korea
| | - Nam-Chul Ha
- Department of Agricultural Biotechnology, and Center for Food Safety and Toxicology, Seoul National University, Seoul, South Korea
| | - Sang Ho Choi
- National Research Laboratory of Molecular Microbiology and Toxicology, Seoul National University, Seoul, South Korea.,Department of Agricultural Biotechnology, and Center for Food Safety and Toxicology, Seoul National University, Seoul, South Korea
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7
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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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8
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Vasieva O, Goryanin I. Is there a Function for a Sex Pheromone Precursor? J Integr Bioinform 2019; 16:/j/jib.ahead-of-print/jib-2019-0016/jib-2019-0016.xml. [PMID: 31301673 PMCID: PMC7074142 DOI: 10.1515/jib-2019-0016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2019] [Accepted: 06/07/2019] [Indexed: 12/29/2022] Open
Abstract
Functional coupling and comparative genomics analysis have been applied to study functional associations of orthologs of enterococcal cAD1 sex pheromone (P13268) known to be responsible for biofilm formation, conjugative plasmid transfer and spreading of bacterial antibiotics resistance. cAD1 peptide pheromone is released from the membrane lipoprotein with the peptide precursor encoded by a gene cad (tr|C2JQE7). Our analysis of genomic neighbourhood of cad and motifs of the encoded polypeptide and its orthologs suggests a close functional association between cAD1 and ApbE protein (Q82Z24), a FMN insertion and trafficking facilitator. The cad and apbE orthologs were coupled in the genomes and ApbE-specific motifs for FMN covalent attachment were identified in cad-encoded protein sequence and its orthologs. These findings suggest a potential role of FMN-based reductase function of the cAD1 lipoprotein precursor in its processing and release of the active sex pheromone peptide. They may lead to a new approach in prevention of antibiotic resistance spread via targeting sex pheromone processing chaperones or by suppression of the FMN availability and covalent binding. This methods can be also applied to a controlled evolution of bacterial pathogenicity in microbial fuel cells, as the findings suggest the crosstalk between bacterial pathogenicity and bacterial electro-activity.
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Affiliation(s)
- O Vasieva
- University of Liverpool, Crown street, Liverpool, UK.,Ingenet ltd, 3d floor, 207 Regent street, London, UK
| | - I Goryanin
- University of Edinburgh, Edinburgh, UK.,Okinawa Institute Science and Technology, Okinawa, Japan.,Tianjin Institute of Industrial Biotechnology, Tianjin, China
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9
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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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10
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Raba DA, Rosas-Lemus M, Menzer WM, Li C, Fang X, Liang P, Tuz K, Minh DDL, Juárez O. Characterization of the Pseudomonas aeruginosa NQR complex, a bacterial proton pump with roles in autopoisoning resistance. J Biol Chem 2018; 293:15664-15677. [PMID: 30135204 DOI: 10.1074/jbc.ra118.003194] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 08/13/2018] [Indexed: 12/22/2022] Open
Abstract
Pseudomonas aeruginosa is a Gram-negative bacterium responsible for a large number of nosocomial infections. The P. aeruginosa respiratory chain contains the ion-pumping NADH:ubiquinone oxidoreductase (NQR). This enzyme couples the transfer of electrons from NADH to ubiquinone to the pumping of sodium ions across the cell membrane, generating a gradient that drives essential cellular processes in many bacteria. In this study, we characterized P. aeruginosa NQR (Pa-NQR) to elucidate its physiologic function. Our analyses reveal that Pa-NQR, in contrast with NQR homologues from other bacterial species, is not a sodium pump, but rather a completely new form of proton pump. Homology modeling and molecular dynamics simulations suggest that cation selectivity could be determined by the exit ion channels. We also show that Pa-NQR is resistant to the inhibitor 2-n-heptyl-4-hydroxyquinoline N-oxide (HQNO). HQNO is a quinolone secreted by P. aeruginosa during infection that acts as a quorum sensing agent and also has bactericidal properties against other bacteria. Using comparative analysis and computational modeling of the ubiquinone-binding site, we identified the specific residues that confer resistance toward this inhibitor. In summary, our findings indicate that Pa-NQR is a proton pump rather than a sodium pump and is highly resistant against the P. aeruginosa-produced compound HQNO, suggesting an important role in the adaptation against autotoxicity. These results provide a deep understanding of the metabolic role of NQR in P. aeruginosa and provide insight into the structural factors that determine the functional specialization in this family of respiratory complexes.
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Affiliation(s)
| | | | - William M Menzer
- From the Departments of Biological Sciences and.,Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616
| | - Chen Li
- Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616
| | - Xuan Fang
- From the Departments of Biological Sciences and
| | | | - Karina Tuz
- From the Departments of Biological Sciences and
| | - David D L Minh
- Chemistry, Illinois Institute of Technology, Chicago, Illinois 60616
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11
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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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