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Rao SN, Kumari GM, Srividya D, Anil HS, Lakshmikanth M, Naik H, Prabhuraj A. Validation of Lon Gene Disruption using Linear DNA Cassette by Crelox Mechanism in E. coli Strains: To Achieve Better Solubility of Putrescine Monooxygenase. Indian J Microbiol 2023; 63:56-64. [PMID: 37188228 PMCID: PMC10172422 DOI: 10.1007/s12088-023-01056-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2022] [Accepted: 01/14/2023] [Indexed: 02/05/2023] Open
Abstract
Numerous expression systems, engineered strains, and cultivation systems have been developed globally but producing recombinant proteins in the soluble form continues to remain a challenge. Escherichia coli, a preferred host for the recombinant production of biopharmaceuticals and other proteins. Up to 75% of human proteins expressed in E. coli have only 25% in an active soluble form. The proteolytic activity of Lon encoded protease triggers the inclusion bodies leading to heterogenous secreted proteins thereby hampering downstream processing and isolation. Putrescine monooxygenases are versatile with applications in iron acquisition, pathogen control, biotransformation, bio-remediation and redox reaction are still isolated from plant and microbial sources at low yields. As a prerequisite to developing protease knockout E. coli strains, using the Cre-loxP recombination strategy we have built a full-length Lon disruption cassette (5'lon-lox66-cre-KanR-lox71-3'lon) (3368 bp) consisting of upstream and downstream regions of Lon, loxP sites, and Cre gene driven by T7 promoter to the expression of Cre recombinase and a selectable kanamycin resistance gene. Here, after the integration of the knock-out cassette into the host genome, we show the production of homogeneous protein species of recombinant Putrescine monooxygenase by using an E. coli platform strain in which Lon gene is deleted. This Lon knock-out strain secreted more homogeneous protein at a volumetric yield of 60% of the wild-type strain. Supplementary Information The online version contains supplementary material available at 10.1007/s12088-023-01056-x.
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Affiliation(s)
- Saroja Narsing Rao
- Pesticide Residue and Food Quality Analysis Laboratory, University of Agricultural Sciences, Raichur, 584104 Karnataka India
| | - G. Monika Kumari
- Pesticide Residue and Food Quality Analysis Laboratory, University of Agricultural Sciences, Raichur, 584104 Karnataka India
| | - D. Srividya
- Pesticide Residue and Food Quality Analysis Laboratory, University of Agricultural Sciences, Raichur, 584104 Karnataka India
| | - H. S. Anil
- Department of Biotechnology, Dayananda Sagar College of Engineering, KS Layout, Shavige Malleswara Hills, Bengaluru-78, Karnataka India
| | - M. Lakshmikanth
- Pesticide Residue and Food Quality Analysis Laboratory, University of Agricultural Sciences, Raichur, 584104 Karnataka India
- College of Agriculture, University of Agricultural Sciences, Raichur, India
| | - Harishchandra Naik
- Pesticide Residue and Food Quality Analysis Laboratory, University of Agricultural Sciences, Raichur, 584104 Karnataka India
| | - A. Prabhuraj
- Pesticide Residue and Food Quality Analysis Laboratory, University of Agricultural Sciences, Raichur, 584104 Karnataka India
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Partipilo M, Yang G, Mascotti ML, Wijma HJ, Slotboom DJ, Fraaije MW. A conserved sequence motif in the E. coli soluble FAD-containing pyridine nucleotide transhydrogenase is important for reaction efficiency. J Biol Chem 2022; 298:102304. [PMID: 35933012 PMCID: PMC9460512 DOI: 10.1016/j.jbc.2022.102304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 07/20/2022] [Accepted: 07/21/2022] [Indexed: 11/06/2022] Open
Abstract
Soluble pyridine nucleotide transhydrogenases (STHs) are flavoenzymes involved in the redox homeostasis of the essential cofactors NAD(H) and NADP(H). They catalyze the reversible transfer of reducing equivalents between the two nicotinamide cofactors. The soluble transhydrogenase from Escherichia coli (SthA) has found wide use in both in vivo and in vitro applications to steer reducing equivalents toward NADPH-requiring reactions. However, mechanistic insight into SthA function is still lacking. In this work, we present a biochemical characterization of SthA, focusing for the first time on the reactivity of the flavoenzyme with molecular oxygen. We report on oxidase activity of SthA that takes place both during transhydrogenation and in the absence of an oxidized nicotinamide cofactor as an electron acceptor. We find that this reaction produces the reactive oxygen species hydrogen peroxide and superoxide anion. Furthermore, we explore the evolutionary significance of the well-conserved CXXXXT motif that distinguishes STHs from the related family of flavoprotein disulfide reductases in which a CXXXXC motif is conserved. Our mutational analysis revealed the cysteine and threonine combination in SthA leads to better coupling efficiency of transhydrogenation and reduced reactive oxygen species release compared to enzyme variants with mutated motifs. These results expand our mechanistic understanding of SthA by highlighting reactivity with molecular oxygen and the importance of the evolutionarily conserved sequence motif.
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Affiliation(s)
- Michele Partipilo
- Membrane Enzymology Group, Groningen Institute of Biomolecular Sciences & Biotechnology, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Guang Yang
- Molecular Enzymology Group, Groningen Institute of Biomolecular Sciences & Biotechnology, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Maria Laura Mascotti
- Molecular Enzymology Group, Groningen Institute of Biomolecular Sciences & Biotechnology, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands; IMIBIO-SL CONICET, Facultad de Química Bioquímica y Farmacia, Universidad Nacional de San Luis, Ejercito de los Andes 950, D5700HHW, San Luis, Argentina
| | - Hein J Wijma
- Molecular Enzymology Group, Groningen Institute of Biomolecular Sciences & Biotechnology, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Dirk Jan Slotboom
- Membrane Enzymology Group, Groningen Institute of Biomolecular Sciences & Biotechnology, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
| | - Marco W Fraaije
- Molecular Enzymology Group, Groningen Institute of Biomolecular Sciences & Biotechnology, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
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Shyam Mohan AH, Rao SN, D S, Rajeswari N. In silico structural, phylogenetic and drug target analysis of putrescine monooxygenase from Shewanella putrefaciens-95. J Genet Eng Biotechnol 2022; 20:57. [PMID: 35412199 PMCID: PMC9005580 DOI: 10.1186/s43141-022-00338-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Accepted: 03/22/2022] [Indexed: 11/10/2022]
Abstract
BACKGROUND The enormous and irresponsible use of antibiotics has led to the emergence of resistant strains of bacteria globally. A new approach to combat this crisis has been nutritional immunity limiting the availability of nutrients to pathogens. Targeting the siderophore biosynthetic pathway that helps in iron acquisition, an essential microelement in the bacterial system has been the topic of interest in recent days that backs the concept of nutritional immunity. Supporting this view, we have chosen to study a key enzyme in the biosynthetic pathway of putrebactin called putrescine monooxygenase (SpPMO) from Shewanella putrefaciens. In our previous study, we co-expressed putrescine monooxygenase recombinantly in Escherichia coli BL21 Star (DE3). The bioinformatic analysis and screening of inhibitors will broaden the scope of SpPMO as a drug target. RESULTS In the present study, we have analysed the physicochemical properties of the target enzyme and other N-hydroxylating monooxygenases (NMOs) using ExPASy server. The target enzyme SpPMO and most of the selected NMOs have a slightly acidic isoelectric point and are medially thermostable and generally insoluble. The multiple sequence alignment identified the GXGXX(N/A), DXXXFATGYXXXXP motives and conserved amino acids involved in FAD binding, NADP binding, secondary structure formation and substrate binding. The phylogenetic analysis indicated the distribution of the monooxygenases into different clades according to their substrate specificity. Further, a 3D model of SpPMO was predicted using I-TASSER online tool with DfoA from Erwinia amylovora as a template. The model was validated using the SAVES server and deposited to the Protein Model Database with the accession number PM0082222. The molecular docking analysis with different substrates revealed the presence of a putrescine binding pocket made of conserved amino acids and another binding pocket present on the surface of the protein wherein all other ligands interact with high binding affinity. The molecular docking of naturally occurring inhibitor molecules with SpPMO 3D model identified curcumin and niazirin with 1.83 and 2.81 μM inhibition constants as two promising inhibitors. Further studies on kinetic parameters of curcumin and niazirin inhibitors in vitro determined the Ki to be 2.6±0.0036 μM and 18.38±0.008 μM respectively. CONCLUSION This analysis will help us understand the structural, phylogenetic and drug target aspects of putrescine monooxygenase from Shewanella putrefaciens-95 in detail. It sheds light on the precautionary measures that can be developed to inhibit the enzyme and thereby the secondary infections caused by them.
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Affiliation(s)
- Anil H Shyam Mohan
- Department of Biotechnology, Dayananda Sagar College of Engineering, Kumaraswamy Layout, Shavige Malleswara Hills, Bengaluru-78, Karnataka, India
| | - Saroja Narsing Rao
- Pesticide Residue and Food Quality Analysis Laboratory, University of Agricultural Sciences, Raichur, Karnataka, 584104, India.
| | - Srividya D
- Department of Biotechnology, Davangere University, Shivagangothri, Davangere, Karnataka, 577007, India
| | - N Rajeswari
- Department of Biotechnology, Dayananda Sagar College of Engineering, Kumaraswamy Layout, Shavige Malleswara Hills, Bengaluru-78, Karnataka, India
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Giddings LA, Lountos GT, Kim KW, Brockley M, Needle D, Cherry S, Tropea JE, Waugh DS. Characterization of a broadly specific cadaverine N-hydroxylase involved in desferrioxamine B biosynthesis in Streptomyces sviceus. PLoS One 2021; 16:e0248385. [PMID: 33784308 PMCID: PMC8009421 DOI: 10.1371/journal.pone.0248385] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 02/26/2021] [Indexed: 02/07/2023] Open
Abstract
N-hydroxylating flavin-dependent monooxygenases (FMOs) are involved in the biosynthesis of hydroxamate siderophores, playing a key role in microbial virulence. Herein, we report the first structural and kinetic characterization of a novel alkyl diamine N-hydroxylase DesB from Streptomyces sviceus (SsDesB). This enzyme catalyzes the first committed step in the biosynthesis of desferrioxamine B, a clinical drug used to treat iron overload disorders. X-ray crystal structures of the SsDesB holoenzyme with FAD and the ternary complex with bound NADP+ were solved at 2.86 Å and 2.37 Å resolution, respectively, providing a structural view of the active site environment. SsDesB crystallized as a tetramer and the structure of the individual protomers closely resembles the structures of homologous N-hydroxylating FMOs from Erwinia amylovora (DfoA), Pseudomonas aeruginosa (PvdA), and Aspergillus fumigatus (SidA). Using NADPH oxidation, oxygen consumption, and product formation assays, kinetic parameters were determined for various substrates with SsDesB. SsDesB exhibited typical saturation kinetics with substrate inhibition at high concentrations of NAD(P)H as well as cadaverine. The apparent kcat values for NADPH in steady-state NADPH oxidation and oxygen consumption assays were 0.28 ± 0.01 s-1 and 0.24 ± 0.01 s-1, respectively. However, in product formation assays used to measure the rate of N-hydroxylation, the apparent kcat for NADPH (0.034 ± 0.008 s-1) was almost 10-fold lower under saturating FAD and cadaverine concentrations, reflecting an uncoupled reaction, and the apparent NADPH KM was 33 ± 24 μM. Under saturating FAD and NADPH concentrations, the apparent kcat and KM for cadaverine in Csaky assays were 0.048 ± 0.004 s-1 and 19 ± 9 μM, respectively. SsDesB also N-hydroxylated putrescine, spermidine, and L-lysine substrates but not alkyl (di)amines that were branched or had fewer than four methylene units in an alkyl chain. These data demonstrate that SsDesB has wider substrate scope compared to other well-studied ornithine and lysine N-hydroxylases, making it an amenable biocatalyst for the production of desferrioxamine B, derivatives, and other N-substituted products.
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Affiliation(s)
- Lesley-Ann Giddings
- Department of Chemistry, Smith College, Northampton, MA, United States of America
- Department of Chemistry & Biochemistry, Middlebury College, Middlebury, VT, United States of America
| | - George T. Lountos
- Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, MD, United States of America
| | - Kang Woo Kim
- Department of Chemistry & Biochemistry, Middlebury College, Middlebury, VT, United States of America
| | - Matthew Brockley
- Department of Chemistry & Biochemistry, Middlebury College, Middlebury, VT, United States of America
| | - Danielle Needle
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD, United States of America
| | - Scott Cherry
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD, United States of America
| | - Joseph E. Tropea
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD, United States of America
| | - David S. Waugh
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD, United States of America
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Li H, Forson B, Eckshtain-Levi M, Valentino H, Martín Del Campo JS, Tanner JJ, Sobrado P. Biochemical Characterization of the Two-Component Flavin-Dependent Monooxygenase Involved in Valanimycin Biosynthesis. Biochemistry 2020; 60:31-40. [PMID: 33350810 DOI: 10.1021/acs.biochem.0c00679] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The flavin reductase (FRED) and isobutylamine N-hydroxylase (IBAH) from Streptomyces viridifaciens constitute a two-component, flavin-dependent monooxygenase system that catalyzes the first step in valanimycin biosynthesis. FRED is an oxidoreductase that provides the reduced flavin to IBAH, which then catalyzes the hydroxylation of isobutylamine (IBA) to isobutylhydroxylamine (IBHA). In this work, we used several complementary methods to investigate FAD binding, steady-state and rapid reaction kinetics, and enzyme-enzyme interactions in the FRED:IBAH system. The affinity of FRED for FADox is higher than its affinity for FADred, consistent with its function as a flavin reductase. Conversely, IBAH binds FADred more tightly than FADox, consistent with its role as a monooxygenase. FRED exhibits a strong preference (28-fold) for NADPH over NADH as the electron source for FAD reduction. Isothermal titration calorimetry was used to study the association of FRED and IBAH. In the presence of FAD, either oxidized or reduced, FRED and IBAH associate with a dissociation constant of 7-8 μM. No interaction was observed in the absence of FAD. These results are consistent with the formation of a protein-protein complex for direct transfer of reduced flavin from the reductase to the monooxygenase in this two-component system.
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Affiliation(s)
- Hao Li
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Benedicta Forson
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Meital Eckshtain-Levi
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Hannah Valentino
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
| | | | - John J Tanner
- Departments of Biochemistry and Chemistry, University of Missouri, Columbia, Missouri 65211, United States
| | - Pablo Sobrado
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States.,Center for Drug Discovery, Virginia Tech, Blacksburg, Virginia 24061, United States
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Maglangit F, Alrashdi S, Renault J, Trembleau L, Victoria C, Tong MH, Wang S, Kyeremeh K, Deng H. Characterization of the promiscuous N-acyl CoA transferase, LgoC, in legonoxamine biosynthesis. Org Biomol Chem 2020; 18:2219-2222. [DOI: 10.1039/d0ob00320d] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
More than 500 siderophores are known to date, but only three were identified to be aryl-containing hydroxamate siderophores, legonoxamines A and B from Streptomyces sp. MA37, and aryl ferrioxamine 2 from Micrococcus luteus KLE1011.
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Affiliation(s)
- Fleurdeliz Maglangit
- Marine Biodiscovery Centre
- Department of Chemistry
- University of Aberdeen
- Aberdeen AB24 3UE
- UK
| | - Saad Alrashdi
- Marine Biodiscovery Centre
- Department of Chemistry
- University of Aberdeen
- Aberdeen AB24 3UE
- UK
| | | | - Laurent Trembleau
- Marine Biodiscovery Centre
- Department of Chemistry
- University of Aberdeen
- Aberdeen AB24 3UE
- UK
| | - Catherine Victoria
- Institute of Organic Chemistry
- Leibniz University Hannover
- Schneiderberg 1B
- Germany
| | - Ming Him Tong
- Marine Biodiscovery Centre
- Department of Chemistry
- University of Aberdeen
- Aberdeen AB24 3UE
- UK
| | - Shan Wang
- Marine Biodiscovery Centre
- Department of Chemistry
- University of Aberdeen
- Aberdeen AB24 3UE
- UK
| | - Kwaku Kyeremeh
- Marine and Plant Research Laboratory of Ghana
- Department of Chemistry
- University of Ghana
- P.O. Box LG56
- Ghana
| | - Hai Deng
- Marine Biodiscovery Centre
- Department of Chemistry
- University of Aberdeen
- Aberdeen AB24 3UE
- UK
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Saroja NR, Mohan AHS, Srividya D, Supreetha K. Chaperone-assisted expression and purification of putrescine monooxygenase from Shewanella putrefaciens-95. Protein Expr Purif 2019; 157:9-16. [PMID: 30654014 DOI: 10.1016/j.pep.2019.01.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2018] [Revised: 01/09/2019] [Accepted: 01/09/2019] [Indexed: 01/22/2023]
Abstract
A putrescine monooxygenase from Shewanella putrefaciens 95 (SpPMO) is the initial enzyme catalyzing the hydroxylation of putrescine to N-hydroxyl putrescine, the precursor for the synthesis of a siderophore putrebactin was identified. This PMO clustered together with known characterized NMOs from Shewanella baltica, Bordetella pertussis, Erwinia amylovora, Streptomyces sp. Gordonia rubripertincta, Pseudomonas aeruginosa and outgrouped from Escherichia coli, Nocardia farcinica, and Rhodococcus erythropolis. The deduced SpPMO protein showed 53% and 36% sequence identity with other characterized bacterial NMOs from Erwinia amylovora and Gordonia rubripertincta respectively. In this investigation, we have cloned the complete 1518bp coding sequence of pubA from Shewanella putrefaciens 95 encoding the corresponding protein SpPMO. It comprises 505 amino acid residues in length and has approximately a molecular weight of 54 kDa. Chaperone-assisted heterologous expression of SpPMO in pET151Topo expression vector under the control of bacteriophage T7 promoter permitted a stringent IPTG dependent expression. It has been successfully cloned, overexpressed and purified as a soluble His6 -tagged enzyme using E. coli as a cloning and expression host. The expression of recombinant SpPMO was confirmed by Western blotting using anti-His6 antibody. The purified protein showed FAD and NADPH dependent N-hydroxylation activity. This study has paved a way to understand the hydroxylation step of putrebactin synthesis which can be further investigated by studying its kinetic mechanism and physiological role.
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Affiliation(s)
- Narsing Rao Saroja
- Pesticide Residue and Food Quality Analysis Laboratory, University of Agricultural Sciences, Raichur, 584104, Karnataka, India.
| | - Anil H Shyam Mohan
- Department of Biotechnology, Dayananda Sagar College of Engineering, Kumaraswamy Layout, Shavige Malleswara Hills, Bengaluru, 78, Karnataka, India
| | - D Srividya
- Pesticide Residue and Food Quality Analysis Laboratory, University of Agricultural Sciences, Raichur, 584104, Karnataka, India
| | - K Supreetha
- Department of Biotechnology, Dayananda Sagar College of Engineering, Kumaraswamy Layout, Shavige Malleswara Hills, Bengaluru, 78, Karnataka, India
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Romero E, Gómez Castellanos JR, Gadda G, Fraaije MW, Mattevi A. Same Substrate, Many Reactions: Oxygen Activation in Flavoenzymes. Chem Rev 2018; 118:1742-1769. [DOI: 10.1021/acs.chemrev.7b00650] [Citation(s) in RCA: 216] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Elvira Romero
- Molecular Enzymology Group, University of Groningen, Nijenborgh 4, 9747AG Groningen, The Netherlands
| | - J. Rubén Gómez Castellanos
- Department of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, Via Ferrata 9, 27100 Pavia, Italy
| | - Giovanni Gadda
- Departments of Chemistry and Biology, Center for Diagnostics and Therapeutics, and Center for Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia 30302-3965, United States
| | - Marco W. Fraaije
- Molecular Enzymology Group, University of Groningen, Nijenborgh 4, 9747AG Groningen, The Netherlands
| | - Andrea Mattevi
- Department of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, Via Ferrata 9, 27100 Pavia, Italy
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Bufkin K, Sobrado P. Characterization of the Ornithine Hydroxylation Step in Albachelin Biosynthesis. Molecules 2017; 22:E1652. [PMID: 28974024 PMCID: PMC6151521 DOI: 10.3390/molecules22101652] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Revised: 09/27/2017] [Accepted: 09/28/2017] [Indexed: 11/16/2022] Open
Abstract
N-Hydroxylating monooxygenases (NMOs) are involved in siderophore biosynthesis. Siderophores are high affinity iron chelators composed of catechol and hydroxamate functional groups that are synthesized and secreted by microorganisms and plants. Recently, a new siderophore named albachelin was isolated from a culture of Amycolatopsis alba growing under iron-limiting conditions. This work focuses on the expression, purification, and characterization of the NMO, abachelin monooxygenase (AMO) from A. alba. This enzyme was purified and characterized in its holo (FAD-bound) and apo (FAD-free) forms. The apo-AMO could be reconstituted by addition of free FAD. The two forms of AMO hydroxylate ornithine, while lysine increases oxidase activity but is not hydroxylated and display low affinity for NADPH.
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Affiliation(s)
- Kendra Bufkin
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA.
| | - Pablo Sobrado
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA.
- Center for Drug Discovery, Virginia Tech, Blacksburg, VA 24061, USA.
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10
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Martín del Campo JS, Vogelaar N, Tolani K, Kizjakina K, Harich K, Sobrado P. Inhibition of the Flavin-Dependent Monooxygenase Siderophore A (SidA) Blocks Siderophore Biosynthesis and Aspergillus fumigatus Growth. ACS Chem Biol 2016; 11:3035-3042. [PMID: 27588426 DOI: 10.1021/acschembio.6b00666] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Aspergillus fumigatus is an opportunistic fungal pathogen and the most common causative agent of fatal invasive mycoses. The flavin-dependent monooxygenase siderophore A (SidA) catalyzes the oxygen and NADPH dependent hydroxylation of l-ornithine (l-Orn) to N5-l-hydroxyornithine in the biosynthetic pathway of hydroxamate-containing siderophores in A. fumigatus. Deletion of the gene that codes for SidA has shown that it is essential in establishing infection in mice models. Here, a fluorescence polarization high-throughput assay was used to screen a 2320 compound library for inhibitors of SidA. Celastrol, a natural quinone methide, was identified as a noncompetitive inhibitor of SidA with a MIC value of 2 μM. Docking experiments suggest that celastrol binds across the NADPH and l-Orn pocket. Celastrol prevents A. fumigatus growth in blood agar. The addition of purified ferric-siderophore abolished the inhibitory effect of celastrol. Thus, celastrol inhibits A. fumigatus growth by blocking siderophore biosynthesis through SidA inhibiton.
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Affiliation(s)
| | - Nancy Vogelaar
- Virginia
Tech Center for Drug Discovery, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Karishma Tolani
- Department
of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Karina Kizjakina
- Department
of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Kim Harich
- Department
of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Pablo Sobrado
- Department
of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
- Virginia
Tech Center for Drug Discovery, Virginia Tech, Blacksburg, Virginia 24061, United States
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11
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Abdelwahab H, Robinson R, Rodriguez P, Adly C, El-Sohaimy S, Sobrado P. Identification of structural determinants of NAD(P)H selectivity and lysine binding in lysine N(6)-monooxygenase. Arch Biochem Biophys 2016; 606:180-8. [PMID: 27503802 DOI: 10.1016/j.abb.2016.08.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 07/22/2016] [Accepted: 08/01/2016] [Indexed: 11/26/2022]
Abstract
l-lysine (l-Lys) N(6)-monooxygenase (NbtG), from Nocardia farcinica, is a flavin-dependent enzyme that catalyzes the hydroxylation of l-Lys in the presence of oxygen and NAD(P)H in the biosynthetic pathway of the siderophore nocobactin. NbtG displays only a 3-fold preference for NADPH over NADH, different from well-characterized related enzymes, which are highly selective for NADPH. The structure of NbtG with bound NAD(P)(+) or l-Lys is currently not available. Herein, we present a mutagenesis study targeting M239, R301, and E216. These amino acids are conserved and located in either the NAD(P)H binding domain or the l-Lys binding pocket. M239R resulted in high production of hydrogen peroxide and little hydroxylation with no change in coenzyme selectivity. R301A caused a 300-fold decrease on kcat/Km value with NADPH but no change with NADH. E216Q increased the Km value for l-Lys by 30-fold with very little change on the kcat value or in the binding of NAD(P)H. These results suggest that R301 plays a major role in NADPH selectivity by interacting with the 2'-phosphate of the adenine-ribose moiety of NADPH, while E216 plays a role in l-Lys binding.
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Affiliation(s)
- Heba Abdelwahab
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA; Department of Chemistry, Faculty of Science, Damietta University, Damietta, 34517, Egypt
| | - Reeder Robinson
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA
| | - Pedro Rodriguez
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA
| | - Camelia Adly
- Department of Chemistry, Faculty of Science, Damietta University, Damietta, 34517, Egypt
| | - Sohby El-Sohaimy
- Department of Food Technology, Arid Lands Cultivation Research Institute, City of Scientific Research and Technological Applications, Alexandria, 21934, Egypt
| | - Pablo Sobrado
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA; Fralin Life Science Institute, Virginia Tech, Blacksburg, VA 24061, USA; Virginia Tech Center for Drug Discovery, Virginia Tech, Blacksburg, VA 24061, USA.
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Robinson R, Qureshi IA, Klancher CA, Rodriguez PJ, Tanner JJ, Sobrado P. Contribution to catalysis of ornithine binding residues in ornithine N5-monooxygenase. Arch Biochem Biophys 2015; 585:25-31. [PMID: 26375201 PMCID: PMC6467063 DOI: 10.1016/j.abb.2015.09.008] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Revised: 08/22/2015] [Accepted: 09/10/2015] [Indexed: 10/23/2022]
Abstract
The SidA ornithine N5-monooxygenase from Aspergillus fumigatus is a flavin monooxygenase that catalyzes the NADPH-dependent hydroxylation of ornithine. Herein we report a mutagenesis study targeting four residues that contact ornithine in crystal structures of SidA: Lys107, Asn293, Asn323, and Ser469. Mutation of Lys107 to Ala abolishes activity as measured in steady-state oxygen consumption and ornithine hydroxylation assays, indicating that the ionic interaction of Lys107 with the carboxylate of ornithine is essential for catalysis. Mutation of Asn293, Asn323, or Ser469 individually to Ala results in >14-fold increases in Km values for ornithine. Asn323 to Ala also increases the rate constant for flavin reduction by NADPH by 18-fold. Asn323 is unique among the four ornithine binding residues in that it also interacts with NADPH by forming a hydrogen bond with the nicotinamide ribose. The crystal structure of N323A complexed with NADP(+) and ornithine shows that the nicontinamide riboside group of NADP is disordered. This result suggests that the increase in flavin reduction rate results from an increase in conformational space available to the enzyme-bound NADP(H). Asn323 thus facilitates ornithine binding at the expense of hindering flavin reduction, which demonstrates the delicate balance that exists within protein-ligand interaction networks in enzyme active sites.
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Affiliation(s)
- Reeder Robinson
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA
| | - Insaf A Qureshi
- Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India
| | | | - Pedro J Rodriguez
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA
| | - John J Tanner
- Departments of Biochemistry and Chemistry, University of Missouri-Columbia, Columbia, MO 65211, USA.
| | - Pablo Sobrado
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA.
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13
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Binda C, Robinson RM, Martin Del Campo JS, Keul ND, Rodriguez PJ, Robinson HH, Mattevi A, Sobrado P. An unprecedented NADPH domain conformation in lysine monooxygenase NbtG provides insights into uncoupling of oxygen consumption from substrate hydroxylation. J Biol Chem 2015; 290:12676-88. [PMID: 25802330 DOI: 10.1074/jbc.m114.629485] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Indexed: 01/01/2023] Open
Abstract
N-Hydroxylating monooxygenases are involved in the biosynthesis of iron-chelating hydroxamate-containing siderophores that play a role in microbial virulence. These flavoenzymes catalyze the NADPH- and oxygen-dependent hydroxylation of amines such as those found on the side chains of lysine and ornithine. In this work we report the biochemical and structural characterization of Nocardia farcinica Lys monooxygenase (NbtG), which has similar biochemical properties to mycobacterial homologs. NbtG is also active on d-Lys, although it binds l-Lys with a higher affinity. Differently from the ornithine monooxygenases PvdA, SidA, and KtzI, NbtG can use both NADH and NADPH and is highly uncoupled, producing more superoxide and hydrogen peroxide than hydroxylated Lys. The crystal structure of NbtG solved at 2.4 Å resolution revealed an unexpected protein conformation with a 30° rotation of the NAD(P)H domain with respect to the flavin adenine dinucleotide (FAD) domain that precludes binding of the nicotinamide cofactor. This "occluded" structure may explain the biochemical properties of NbtG, specifically with regard to the substantial uncoupling and limited stabilization of the C4a-hydroperoxyflavin intermediate. Biological implications of these findings are discussed.
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Affiliation(s)
- Claudia Binda
- From the Department of Biology and Biotechnology, University of Pavia, Pavia 27100, Italy
| | - Reeder M Robinson
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, and
| | | | - Nicholas D Keul
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, and
| | - Pedro J Rodriguez
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, and
| | - Howard H Robinson
- Biology Department, Brookhaven National Laboratory, Upton, New York 11973
| | - Andrea Mattevi
- From the Department of Biology and Biotechnology, University of Pavia, Pavia 27100, Italy,
| | - Pablo Sobrado
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, and
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14
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Setser JW, Heemstra JR, Walsh CT, Drennan CL. Crystallographic evidence of drastic conformational changes in the active site of a flavin-dependent N-hydroxylase. Biochemistry 2014; 53:6063-77. [PMID: 25184411 PMCID: PMC4179590 DOI: 10.1021/bi500655q] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
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The soil actinomycete Kutzneria sp. 744 produces
a class of highly decorated hexadepsipeptides, which represent a new
chemical scaffold that has both antimicrobial and antifungal properties.
These natural products, known as kutznerides, are created via nonribosomal
peptide synthesis using various derivatized amino acids. The piperazic
acid moiety contained in the kutzneride scaffold, which is vital for
its antibiotic activity, has been shown to derive from the hydroxylated
product of l-ornithine, l-N5-hydroxyornithine. The production of this hydroxylated species
is catalyzed by the action of an FAD- and NAD(P)H-dependent N-hydroxylase known as KtzI. We have been able to structurally
characterize KtzI in several states along its catalytic trajectory,
and by pairing these snapshots with the biochemical and structural
data already available for this enzyme class, we propose a structurally
based reaction mechanism that includes novel conformational changes
of both the protein backbone and the flavin cofactor. Further, we
were able to recapitulate these conformational changes in the protein
crystal, displaying their chemical competence. Our series of structures,
with corroborating biochemical and spectroscopic data collected by
us and others, affords mechanistic insight into this relatively new
class of flavin-dependent hydroxylases and adds another layer to the
complexity of flavoenzymes.
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Affiliation(s)
- Jeremy W Setser
- Department of Chemistry, ‡Department of Biology, and §Howard Hughes Medical Institute, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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15
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Robinson RM, Rodriguez PJ, Sobrado P. Mechanistic studies on the flavin-dependent N⁶-lysine monooxygenase MbsG reveal an unusual control for catalysis. Arch Biochem Biophys 2014; 550-551:58-66. [PMID: 24769337 DOI: 10.1016/j.abb.2014.04.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Revised: 04/10/2014] [Accepted: 04/15/2014] [Indexed: 10/25/2022]
Abstract
The mechanism of Mycobacterium smegmatis G (MbsG), a flavin-dependent l-lysine monooxygenase, was investigated under steady-state and rapid reaction conditions using primary and solvent kinetic isotope effects, substrate analogs, pH and solvent viscosity effects as mechanistic probes. The results suggest that l-lysine binds before NAD(P)H, which leads to a decrease in the rate constant for flavin reduction. l-lysine binding has no effect on the rate of flavin oxidation, which occurs in a one-step process without the observation of a C4a-hydroperoxyflavin intermediate. Similar effects were determined with several substrate analogs. Flavin oxidation is pH independent while the kcat/Km and kred/KD pH profiles for NAD(P)H exhibit single pKa values of ∼6.0, with increasing activity as the pH decreases. At lower pH, the enzyme becomes more uncoupled, producing more hydrogen peroxide and superoxide. Hydride transfer is partially rate-limiting at neutral pH and becomes more rate-limiting at low pH. An inverse solvent viscosity effect on kcat/Km for NAD(P)H was observed at neutral pH whereas a normal solvent viscosity effect was observed at lower pH. Together, the results indicate a unique mechanism where a rate-limiting and pH-sensitive conformational change occurs in the reductive half-reaction, which affects the efficiency of lysine hydroxylation.
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Affiliation(s)
- Reeder M Robinson
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA; Fralin Life Science Institute, Virginia Tech, Blacksburg, VA 24061, USA
| | - Pedro J Rodriguez
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA; Fralin Life Science Institute, Virginia Tech, Blacksburg, VA 24061, USA
| | - Pablo Sobrado
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA; Fralin Life Science Institute, Virginia Tech, Blacksburg, VA 24061, USA; Virginia Tech Center for Drug Discovery, Virginia Tech, Blacksburg, VA 24061, USA.
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16
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Robinson R, Franceschini S, Fedkenheuer M, Rodriguez PJ, Ellerbrock J, Romero E, Echandi MP, Martin Del Campo JS, Sobrado P. Arg279 is the key regulator of coenzyme selectivity in the flavin-dependent ornithine monooxygenase SidA. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2014; 1844:778-84. [PMID: 24534646 DOI: 10.1016/j.bbapap.2014.02.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Revised: 01/29/2014] [Accepted: 02/06/2014] [Indexed: 10/25/2022]
Abstract
Siderophore A (SidA) is a flavin-dependent monooxygenase that catalyzes the NAD(P)H- and oxygen-dependent hydroxylation of ornithine in the biosynthesis of siderophores in Aspergillus fumigatus and is essential for virulence. SidA can utilize both NADPH or NADH for activity; however, the enzyme is selective for NADPH. Structural analysis shows that R279 interacts with the 2'-phosphate of NADPH. To probe the role of electrostatic interactions in coenzyme selectivity, R279 was mutated to both an alanine and a glutamate. The mutant proteins were active but highly uncoupled, oxidizing NADPH and producing hydrogen peroxide instead of hydroxylated ornithine. For wtSidA, the catalytic efficiency was 6-fold higher with NADPH as compared to NADH. For the R279A mutant the catalytic efficiency was the same with both coenyzmes, while for the R279E mutant the catalytic efficiency was 5-fold higher with NADH. The effects are mainly due to an increase in the KD values, as no major changes on the kcat or flavin reduction values were observed. Thus, the absence of a positive charge leads to no coenzyme selectivity while introduction of a negative charge leads to preference for NADH. Flavin fluorescence studies suggest altered interaction between the flavin and NADP⁺ in the mutant enzymes. The effects are caused by different binding modes of the coenzyme upon removal of the positive charge at position 279, as no major conformational changes were observed in the structure for R279A. The results indicate that the positive charge at position 279 is critical for tight binding of NADPH and efficient hydroxylation.
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Affiliation(s)
- Reeder Robinson
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, United States
| | - Stefano Franceschini
- Department of Biology and Biotechnology, University of Pavia, Via Ferrata 9, 27100, Italy
| | - Michael Fedkenheuer
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, United States
| | - Pedro J Rodriguez
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, United States
| | - Jacob Ellerbrock
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, United States
| | - Elvira Romero
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, United States
| | | | | | - Pablo Sobrado
- Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, United States; Virginia Tech Center for Drug Discovery, Virginia Tech, Blacksburg, VA 24061, United States.
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17
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Shirey C, Badieyan S, Sobrado P. Role of Ser-257 in the sliding mechanism of NADP(H) in the reaction catalyzed by the Aspergillus fumigatus flavin-dependent ornithine N5-monooxygenase SidA. J Biol Chem 2013; 288:32440-32448. [PMID: 24072704 DOI: 10.1074/jbc.m113.487181] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
SidA (siderophore A) is a flavin-dependent N-hydroxylating monooxygenase that is essential for virulence in Aspergillus fumigatus. SidA catalyzes the NADPH- and oxygen-dependent formation of N(5)-hydroxyornithine. In this reaction, NADPH reduces the flavin, and the resulting NADP(+) is the last product to be released. The presence of NADP(+) is essential for activity, as it is required for stabilization of the C4a-hydroperoxyflavin, which is the hydroxylating species. As part of our efforts to determine the molecular details of the role of NADP(H) in catalysis, we targeted Ser-257 for site-directed mutagenesis and performed extensive characterization of the S257A enzyme. Using a combination of steady-state and stopped-flow kinetic experiments, substrate analogs, and primary kinetic isotope effects, we show that the interaction between Ser-257 and NADP(H) is essential for stabilization of the C4a-hydroperoxyflavin. Molecular dynamics simulation results suggest that Ser-257 functions as a pivot point, allowing the nicotinamide of NADP(+) to slide into position for stabilization of the C4a-hydroperoxyflavin.
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Affiliation(s)
| | | | - Pablo Sobrado
- From the Department of Biochemistry; the Virginia Tech Center for Drug Discovery, Virginia Tech, Blacksburg, Virginia 24061.
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18
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Potential implication of the chemical properties and bioactivity of nitrone spin traps for therapeutics. Future Med Chem 2012; 4:1171-207. [PMID: 22709256 DOI: 10.4155/fmc.12.74] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Nitrone therapeutics has been employed in the treatment of oxidative stress-related diseases such as neurodegeneration, cardiovascular disease and cancer. The nitrone-based compound NXY-059, which is the first drug to reach clinical trials for the treatment of acute ischemic stroke, has provided promise for the development of more robust pharmacological agents. However, the specific mechanism of nitrone bioactivity remains unclear. In this review, we present a variety of nitrone chemistry and biological activity that could be implicated for the nitrone's pharmacological activity. The chemistries of spin trapping and spin adduct reveal insights on the possible roles of nitrones for altering cellular redox status through radical scavenging or nitric oxide donation, and their biological effects are presented. An interdisciplinary approach towards the development of novel synthetic antioxidants with improved pharmacological properties encompassing theoretical, synthetic, biochemical and in vitro/in vivo studies is covered.
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Analyses of MbtB, MbtE, and MbtF suggest revisions to the mycobactin biosynthesis pathway in Mycobacterium tuberculosis. J Bacteriol 2012; 194:2809-18. [PMID: 22447909 DOI: 10.1128/jb.00088-12] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The production of mycobactin (MBT) by Mycobacterium tuberculosis is essential for this bacterium to access iron when it is in an infected host. Due to this essential function, there is considerable interest in deciphering the mechanism of MBT assembly, with the goal of targeting select biosynthetic steps for antituberculosis drug development. The proposed scheme for MBT biosynthesis involves assembly of the MBT backbone by a hybrid nonribosomal peptide synthetase (NRPS)/polyketide synthase (PKS) megasynthase followed by the tailoring of this backbone by N(6) acylation of the central l-Lys residue and subsequent N(6)-hydroxylation of the central N(6)-acyl-l-Lys and the terminal caprolactam. A complete testing of this hypothesis has been hindered by the inability to heterologously produce soluble megasynthase components. Here we show that soluble forms of the NRPS components MbtB, MbtE, and MbtF are obtained when these enzymes are coproduced with MbtH. Using these soluble enzymes we determined the amino acid specificity of each adenylation (A) domain. These results suggest that the proposed tailoring enzymes are actually involved in precursor biosynthesis since the A domains of MbtE and MbtF are specific for N(6)-acyl-N(6)-hydroxy-l-Lys and N(6)-hydroxy-l-Lys, respectively. Furthermore, the preference of the A domain of MbtB for l-Thr over l-Ser suggests that the megasynthase produces MBT derivatives with β-methyl oxazoline rings. Since the most prominent form of MBT produced by M. tuberculosis lacks this β-methyl group, a mechanism for demethylation remains to be discovered. These results suggest revisions to the MBT biosynthesis pathway while also identifying new targets for antituberculosis drug development.
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20
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Qi J, Kizjakina K, Robinson R, Tolani K, Sobrado P. A fluorescence polarization binding assay to identify inhibitors of flavin-dependent monooxygenases. Anal Biochem 2012; 425:80-7. [PMID: 22410281 DOI: 10.1016/j.ab.2012.03.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Revised: 02/24/2012] [Accepted: 03/03/2012] [Indexed: 10/28/2022]
Abstract
N-Hydroxylating monooxygenases (NMOs) are essential for pathogenesis in fungi and bacteria. NMOs catalyze the hydroxylation of sine and ornithine in the biosynthesis of hydroxamate-containing siderophores. Inhibition of kynurenine monooxygenase (KMO), which catalyzes the conversion of kynurenine to 3-hydroxykynurenine, alleviates neurodegenerative disorders such as Huntington's and Alzheimer's diseases and brain infections caused by the parasite Trypanosoma brucei. These enzymes are examples of flavin-dependent monooxygenases, which are validated drug targets. Here, we describe the development and optimization of a fluorescence polarization assay to identify potential inhibitors of flavin-dependent monooxygenases. Fluorescently labeled ADP molecules were synthesized and tested. An ADP-TAMRA chromophore bound to KMO with a K(d) value of 0.60 ± 0.05 μM and to the NMOs from Aspergillus fumigatus and Mycobacterium smegmatis with K(d) values of 2.1 ± 0.2 and 4.0 ± 0.2 μM, respectively. The assay was tested in competitive binding experiments with substrates and products of KMO and an NMO. Furthermore, we show that this assay can be used to identify inhibitors of NMOs. A Z' factor of 0.77 was calculated, and we show that the assay exhibits good tolerance to temperature, incubation time, and dimethyl sulfoxide concentration.
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Affiliation(s)
- Jun Qi
- Department of Biochemistry, Virginia Tech, Blacksburg, 24061, USA
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