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Delavari N, Zhang Z, Stull F. Rapid reaction studies on the chemistry of flavin oxidation in urocanate reductase. J Biol Chem 2024; 300:105689. [PMID: 38280427 PMCID: PMC10882135 DOI: 10.1016/j.jbc.2024.105689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 01/19/2024] [Accepted: 01/21/2024] [Indexed: 01/29/2024] Open
Abstract
Urocanate reductase (UrdA) is a bacterial flavin-dependent enzyme that reduces urocanate to imidazole propionate, enabling bacteria to use urocanate as an alternative respiratory electron acceptor. Elevated serum levels of imidazole propionate are associated with the development of type 2 diabetes, and, since UrdA is only present in humans in gut bacteria, this enzyme has emerged as a significant factor linking the health of the gut microbiome and insulin resistance. Here, we investigated the chemistry of flavin oxidation by urocanate in the isolated FAD domain of UrdA (UrdA') using anaerobic stopped-flow experiments. This analysis unveiled the presence of a charge-transfer complex between reduced FAD and urocanate that forms within the dead time of the stopped-flow instrument (∼1 ms), with flavin oxidation subsequently occurring with a rate constant of ∼60 s-1. The pH dependence of the reaction and analysis of an Arg411Ala mutant of UrdA' are consistent with Arg411 playing a crucial role in catalysis by serving as the active site acid that protonates urocanate during hydride transfer from reduced FAD. Mutational analysis of urocanate-binding residues suggests that the twisted conformation of urocanate imposed by the active site of UrdA' facilitates urocanate reduction. Overall, this study provides valuable insight into the mechanism of urocanate reduction by UrdA.
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Affiliation(s)
- Niusha Delavari
- Department of Chemistry, Western Michigan University, Kalamazoo, Michigan, USA
| | - Zhiyao Zhang
- Department of Chemistry, Western Michigan University, Kalamazoo, Michigan, USA
| | - Frederick Stull
- Department of Chemistry, Western Michigan University, Kalamazoo, Michigan, USA.
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2
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Baquero DP, Cvirkaite-Krupovic V, Hu SS, Fields JL, Liu X, Rensing C, Egelman EH, Krupovic M, Wang F. Extracellular cytochrome nanowires appear to be ubiquitous in prokaryotes. Cell 2023; 186:2853-2864.e8. [PMID: 37290436 PMCID: PMC10330847 DOI: 10.1016/j.cell.2023.05.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 03/04/2023] [Accepted: 05/10/2023] [Indexed: 06/10/2023]
Abstract
Electrically conductive appendages from the anaerobic bacterium Geobacter sulfurreducens, recently identified as extracellular cytochrome nanowires (ECNs), have received wide attention due to numerous potential applications. However, whether other organisms employ similar ECNs for electron transfer remains unknown. Here, using cryoelectron microscopy, we describe the atomic structures of two ECNs from two major orders of hyperthermophilic archaea present in deep-sea hydrothermal vents and terrestrial hot springs. Homologs of Archaeoglobus veneficus ECN are widespread among mesophilic methane-oxidizing Methanoperedenaceae, alkane-degrading Syntrophoarchaeales archaea, and in the recently described megaplasmids called Borgs. The ECN protein subunits lack similarities in their folds; however, they share a common heme arrangement, suggesting an evolutionarily optimized heme packing for efficient electron transfer. The detection of ECNs in archaea suggests that filaments containing closely stacked hemes may be a common and widespread mechanism for long-range electron transfer in both prokaryotic domains of life.
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Affiliation(s)
- Diana P Baquero
- Institut Pasteur, Université Paris Cité, CNRS UMR6047, Archaeal Virology Unit, Paris 75015, France
| | | | - Shengen Shawn Hu
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22903, USA
| | - Jessie Lynda Fields
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35233, USA
| | - Xing Liu
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, Fujian, China
| | - Christopher Rensing
- Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, Fujian, China
| | - Edward H Egelman
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22903, USA.
| | - Mart Krupovic
- Institut Pasteur, Université Paris Cité, CNRS UMR6047, Archaeal Virology Unit, Paris 75015, France.
| | - Fengbin Wang
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22903, USA; Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35233, USA; O'Neal Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL 35233, USA.
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3
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Curtolo F, Arantes GM. Dissecting Reaction Mechanisms and Catalytic Contributions in Flavoprotein Fumarate Reductases. J Chem Inf Model 2023. [PMID: 37196341 DOI: 10.1021/acs.jcim.3c00292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The interconversion between fumarate and succinate is fundamental to the energy metabolism of nearly all organisms. This redox reaction is catalyzed by a large family of enzymes, fumarate reductases and succinate dehydrogenases, using hydride and proton transfers from a flavin cofactor and a conserved Arg side-chain. These flavoenzymes also have substantial biomedical and biotechnological importance. Therefore, a detailed understanding of their catalytic mechanisms is valuable. Here, calibrated electronic structure calculations in a cluster model of the active site of the Fcc3 fumarate reductase were employed to investigate various reaction pathways and possible intermediates in the enzymatic environment and to dissect interactions that contribute to catalysis of fumarate reduction. Carbanion, covalent adduct, carbocation, and radical intermediates were examined. Significantly lower barriers were obtained for mechanisms via carbanion intermediates, with similar activation energies for hydride and proton transfers. Interestingly, the carbanion bound to the active site is best described as an enolate. Hydride transfer is stabilized by a preorganized charge dipole in the active site and by the restriction of the C1-C2 bond in a twisted conformation of the otherwise planar fumarate dianion. But, protonation of a fumarate carboxylate and quantum tunneling effects are not critical for catalysis of the hydride transfer. Calculations also suggest that the driving force for enzyme turnover is provided by regeneration of the catalytic Arg, either coupled with flavin reduction and decomposition of a proposed transient state or directly from the solvent. The detailed mechanistic description of enzymatic reduction of fumarate provided here clarifies previous contradictory views and provides new insights into catalysis by essential flavoenzyme reductases and dehydrogenases.
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Affiliation(s)
- Felipe Curtolo
- Department of Biochemistry, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, 05508-900 São Paulo, São Paulo, Brazil
| | - Guilherme M Arantes
- Department of Biochemistry, Instituto de Química, Universidade de São Paulo, Av. Prof. Lineu Prestes 748, 05508-900 São Paulo, São Paulo, Brazil
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4
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Iverson TM, Singh PK, Cecchini G. An evolving view of Complex II - non-canonical complexes, megacomplexes, respiration, signaling, and beyond. J Biol Chem 2023; 299:104761. [PMID: 37119852 DOI: 10.1016/j.jbc.2023.104761] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 04/20/2023] [Accepted: 04/22/2023] [Indexed: 05/01/2023] Open
Abstract
Mitochondrial Complex II is traditionally studied for its participation in two key respiratory processes: the electron transport chain and the Krebs cycle. There is now a rich body of literature explaining how Complex II contributes to respiration. However, more recent research shows that not all of the pathologies associated with altered Complex II activity clearly correlate with this respiratory role. Complex II activity has now been shown to be necessary for a range of biological processes peripherally-related to respiration, including metabolic control, inflammation, and cell fate. Integration of findings from multiple types of studies suggests that Complex II both participates in respiration and controls multiple succinate-dependent signal transduction pathways. Thus, the emerging view is that the true biological function of Complex II is well beyond respiration. This review uses a semi-chronological approach to highlight major paradigm shifts that occurred over time. Special emphasis is given to the more recently identified functions of Complex II and its subunits because these findings have infused new directions into an established field.
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Affiliation(s)
- T M Iverson
- Departments of Pharmacology, Vanderbilt University, Nashville, TN 37232; Departments of Biochemistry, Vanderbilt University, Nashville, TN 37232; Departments of Center for Structural Biology, Vanderbilt University, Nashville, TN 37232; Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, TN 37232.
| | - Prashant K Singh
- Departments of Pharmacology, Vanderbilt University, Nashville, TN 37232; Departments of Center for Structural Biology, Vanderbilt University, Nashville, TN 37232
| | - Gary Cecchini
- Molecular Biology Division, San Francisco VA Health Care System, San Francisco, CA 94121; Department of Biochemistry & Biophysics, University of California, San Francisco, CA 94158.
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5
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How an assembly factor enhances covalent FAD attachment to the flavoprotein subunit of complex II. J Biol Chem 2022; 298:102472. [PMID: 36089066 PMCID: PMC9557727 DOI: 10.1016/j.jbc.2022.102472] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 08/31/2022] [Accepted: 09/02/2022] [Indexed: 01/25/2023] Open
Abstract
The membrane-bound complex II family of proteins is composed of enzymes that catalyze succinate and fumarate interconversion coupled with reduction or oxidation of quinones within the membrane domain. The majority of complex II enzymes are protein heterotetramers with the different subunits harboring a variety of redox centers. These redox centers are used to transfer electrons between the site of succinate-fumarate oxidation/reduction and the membrane domain harboring the quinone. A covalently bound FAD cofactor is present in the flavoprotein subunit, and the covalent flavin linkage is absolutely required to enable the enzyme to oxidize succinate. Assembly of the covalent flavin linkage in eukaryotic cells and many bacteria requires additional protein assembly factors. Here, we provide mechanistic details for how the assembly factors work to enhance covalent flavinylation. Both prokaryotic SdhE and mammalian SDHAF2 enhance FAD binding to their respective apoprotein of complex II. These assembly factors also increase the affinity for dicarboxylates to the apoprotein-noncovalent FAD complex and stabilize the preassembly complex. These findings are corroborated by previous investigations of the roles of SdhE in enhancing covalent flavinylation in both bacterial succinate dehydrogenase and fumarate reductase flavoprotein subunits and of SDHAF2 in performing the same function for the human mitochondrial succinate dehydrogenase flavoprotein. In conclusion, we provide further insight into assembly factor involvement in building complex II flavoprotein subunit active site required for succinate oxidation.
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6
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Serial crystallography captures dynamic control of sequential electron and proton transfer events in a flavoenzyme. Nat Chem 2022; 14:677-685. [PMID: 35393554 DOI: 10.1038/s41557-022-00922-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Accepted: 02/25/2022] [Indexed: 11/08/2022]
Abstract
Flavin coenzymes are universally found in biological redox reactions. DNA photolyases, with their flavin chromophore (FAD), utilize blue light for DNA repair and photoreduction. The latter process involves two single-electron transfers to FAD with an intermittent protonation step to prime the enzyme active for DNA repair. Here we use time-resolved serial femtosecond X-ray crystallography to describe how light-driven electron transfers trigger subsequent nanosecond-to-microsecond entanglement between FAD and its Asn/Arg-Asp redox sensor triad. We found that this key feature within the photolyase-cryptochrome family regulates FAD re-hybridization and protonation. After first electron transfer, the FAD•- isoalloxazine ring twists strongly when the arginine closes in to stabilize the negative charge. Subsequent breakage of the arginine-aspartate salt bridge allows proton transfer from arginine to FAD•-. Our molecular videos demonstrate how the protein environment of redox cofactors organizes multiple electron/proton transfer events in an ordered fashion, which could be applicable to other redox systems such as photosynthesis.
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Gheorghita AA, Wolfram F, Whitfield GB, Jacobs HM, Pfoh R, Wong SSY, Guitor AK, Goodyear MC, Berezuk AM, Khursigara CM, Parsek MR, Howell PL. The Pseudomonas aeruginosa homeostasis enzyme AlgL clears the periplasmic space of accumulated alginate during polymer biosynthesis. J Biol Chem 2022; 298:101560. [PMID: 34990713 PMCID: PMC8829089 DOI: 10.1016/j.jbc.2021.101560] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 12/27/2021] [Accepted: 12/28/2021] [Indexed: 11/24/2022] Open
Abstract
Pseudomonas aeruginosa is an opportunistic human pathogen and a leading cause of chronic infection in the lungs of individuals with cystic fibrosis. After colonization, P. aeruginosa often undergoes a phenotypic conversion to mucoidy, characterized by overproduction of the alginate exopolysaccharide. This conversion is correlated with poorer patient prognoses. The majority of genes required for alginate synthesis, including the alginate lyase, algL, are located in a single operon. Previous investigations of AlgL have resulted in several divergent hypotheses regarding the protein’s role in alginate production. To address these discrepancies, we determined the structure of AlgL and, using multiple sequence alignments, identified key active site residues involved in alginate binding and catalysis. In vitro enzymatic analysis of active site mutants highlights R249 and Y256 as key residues required for alginate lyase activity. In a genetically engineered P. aeruginosa strain where alginate biosynthesis is under arabinose control, we found that AlgL is required for cell viability and maintaining membrane integrity during alginate production. We demonstrate that AlgL functions as a homeostasis enzyme to clear the periplasmic space of accumulated polymer. Constitutive expression of the AlgU/T sigma factor mitigates the effects of an algL deletion during alginate production, suggesting that an AlgU/T-regulated protein or proteins can compensate for an algL deletion. Together, our study demonstrates the role of AlgL in alginate biosynthesis, explains the discrepancies observed previously across other P. aeruginosa ΔalgL genetic backgrounds, and clarifies the existing divergent data regarding the function of AlgL as an alginate degrading enzyme.
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Affiliation(s)
- Andreea A Gheorghita
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Francis Wolfram
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Gregory B Whitfield
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Holly M Jacobs
- Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, Washington, USA
| | - Roland Pfoh
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Steven S Y Wong
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Allison K Guitor
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Mara C Goodyear
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Alison M Berezuk
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Cezar M Khursigara
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Matthew R Parsek
- Department of Microbiology, University of Washington, Seattle, Washington, USA
| | - P Lynne Howell
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
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8
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Ghosh A, Niland CN, Cahill SM, Karadkhelkar NM, Schramm VL. Mechanism of Triphosphate Hydrolysis by Human MAT2A at 1.07 Å Resolution. J Am Chem Soc 2021; 143:18325-18330. [PMID: 34668717 DOI: 10.1021/jacs.1c09328] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Human methionine adenosyltransferase MAT2A provides S-adenosyl-l-methionine (AdoMet) for methyl-transfer reactions. Epigenetic methylations influence expression patterns in development and in cancer. Transition-state analysis and kinetic studies have described the mechanism of AdoMet and triphosphate formation at the catalytic site. Hydrolysis of triphosphate to pyrophosphate and phosphate by MAT2A is required for product release and proceeds through a second chemical transition state. Crystal structures of MAT2A with analogues of AdoMet and pyrophosphate were obtained in the presence of Mg2+, Al3+, and F-. MgF3- is trapped as a PO3- mimic in a structure with malonate filling the pyrophosphate site. NMR demonstrates that MgF3- and AlF30 are bound by MAT2A as mimics of the departing phosphoryl group. Crystallographic analysis reveals a planar MgF3- acting to mimic a phosphoryl (PO3-) leaving group. The modeled transition state with PO3- has the phosphorus atom sandwiched symmetrically and equidistant (approximately 2 Å) between a pyrophosphate oxygen and the water nucleophile. A catalytic site arginine directs the nucleophilic water to the phosphoryl leaving group. The catalytic geometry of the transition-state reconstruction predicts a loose transition state with characteristics of symmetric nucleophilic displacement.
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Affiliation(s)
- Agnidipta Ghosh
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, United States
| | - Courtney N Niland
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, United States
| | - Sean M Cahill
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, United States
| | - Nishant M Karadkhelkar
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, United States
| | - Vern L Schramm
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, United States
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9
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Gabdulkhakov A, Kolyadenko I, Oliveira P, Tamagnini P, Mikhaylina A, Tishchenko S. The role of positive charged residue in the proton-transfer mechanism of two-domain laccase from Streptomyces griseoflavus Ac-993. J Biomol Struct Dyn 2021; 40:8324-8331. [PMID: 33870857 DOI: 10.1080/07391102.2021.1911852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Multi-copper oxidases are capable of coupling the one-electron oxidation of four substrate equivalents to the four-electron reduction of dioxygen to two molecules of water. This process takes place at the trinuclear copper center of the enzymes. Previously, the main catalytic stages for three-domain (3D) laccases have been identified. However, for bacterial small two-domain (2D) laccases several questions remain to be answered. One of them is the nature of the protonation events upon the reductive cleavage of dioxygen to water. In 3D laccases, acidic residues play a key role in the protonation mechanisms. In this study, the role of the Arg240 residue, located within the T2 tunnel of 2D laccase from Streptomyces griseoflavus Ac-993, was investigated. X-ray structural analysis and kinetic characterization of two mutants, R240A and R240H, have provided support for a role of this residue in the protonation events. Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Azat Gabdulkhakov
- Institute of Protein Research, RAS, Pushchino, Moscow Region, Russia
| | - Ilya Kolyadenko
- Institute of Protein Research, RAS, Pushchino, Moscow Region, Russia
| | - Paulo Oliveira
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.,Departamento de Biologia, Faculdade de Ciências da Universidade do Porto, Porto, Portugal
| | - Paula Tamagnini
- i3S - Instituto de Investigação e Inovação em Saúde, Universidade do Porto, Porto, Portugal.,IBMC - Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.,Departamento de Biologia, Faculdade de Ciências da Universidade do Porto, Porto, Portugal
| | - Alisa Mikhaylina
- Institute of Protein Research, RAS, Pushchino, Moscow Region, Russia
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10
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Stevens DR, Hammes-Schiffer S. Examining the Mechanism of Phosphite Dehydrogenase with Quantum Mechanical/Molecular Mechanical Free Energy Simulations. Biochemistry 2020; 59:943-954. [PMID: 32031785 DOI: 10.1021/acs.biochem.9b01089] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The projected decline of available phosphorus necessitates alternative methods to derive usable phosphate for fertilizer and other applications. Phosphite dehydrogenase oxidizes phosphite to phosphate with the cofactor NAD+ serving as the hydride acceptor. In addition to producing phosphate, this enzyme plays an important role in NADH cofactor regeneration processes. Mixed quantum mechanical/molecular mechanical free energy simulations were performed to elucidate the mechanism of this enzyme and to identify the protonation states of the substrate and product. Specifically, the finite temperature string method with umbrella sampling was used to generate the free energy surfaces and determine the minimum free energy paths for six different initial conditions that varied in the protonation state of the substrate and the position of the nucleophilic water molecule. In contrast to previous studies, the mechanism predicted by all six independent strings is a concerted but asynchronous dissociative mechanism in which hydride transfer from the phosphite substrate to NAD+ occurs prior to attack by the nucleophilic water molecule. His292 is identified as the most likely general base that deprotonates the attacking water molecule. However, Arg237 could also serve as this base if it were deprotonated and His292 were protonated prior to the main chemical transformation, although this scenario is less probable. The simulations indicate that the phosphite substrate is monoanionic in its active form and that the most likely product is dihydrogen phosphate. These mechanistic insights may be helpful for designing mutant enzymes or artificial constructs that convert phosphite to phosphate and NAD+ to NADH more effectively.
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Affiliation(s)
- David R Stevens
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Sharon Hammes-Schiffer
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
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Burke JR, La Clair JJ, Philippe RN, Pabis A, Corbella M, Jez JM, Cortina GA, Kaltenbach M, Bowman ME, Louie GV, Woods KB, Nelson AT, Tawfik DS, Kamerlin SC, Noel JP. Bifunctional Substrate Activation via an Arginine Residue Drives Catalysis in Chalcone Isomerases. ACS Catal 2019. [DOI: 10.1021/acscatal.9b01926] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Jason R. Burke
- Howard Hughes Medical Institute, Jack H. Skirball Center for Chemical Biology and Proteomics, The Salk Institute for Biological Studies, La Jolla, California 92037, United States
| | - James J. La Clair
- Howard Hughes Medical Institute, Jack H. Skirball Center for Chemical Biology and Proteomics, The Salk Institute for Biological Studies, La Jolla, California 92037, United States
| | - Ryan N. Philippe
- Howard Hughes Medical Institute, Jack H. Skirball Center for Chemical Biology and Proteomics, The Salk Institute for Biological Studies, La Jolla, California 92037, United States
| | - Anna Pabis
- Department of Cell and Molecular Biology, Uppsala University, BMC Box 596, S-751 24 Uppsala, Sweden
| | - Marina Corbella
- Department of Chemistry−BMC, Uppsala University, BMC Box 576, S-751 23 Uppsala, Sweden
| | - Joseph M. Jez
- Howard Hughes Medical Institute, Jack H. Skirball Center for Chemical Biology and Proteomics, The Salk Institute for Biological Studies, La Jolla, California 92037, United States
| | - George A. Cortina
- Department of Molecular Physiology and Biomedical Engineering, University of Virginia, Charlottesville, Virginia 22903, United States
| | - Miriam Kaltenbach
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Marianne E. Bowman
- Howard Hughes Medical Institute, Jack H. Skirball Center for Chemical Biology and Proteomics, The Salk Institute for Biological Studies, La Jolla, California 92037, United States
| | - Gordon V. Louie
- Howard Hughes Medical Institute, Jack H. Skirball Center for Chemical Biology and Proteomics, The Salk Institute for Biological Studies, La Jolla, California 92037, United States
| | - Katherine B. Woods
- Howard Hughes Medical Institute, Jack H. Skirball Center for Chemical Biology and Proteomics, The Salk Institute for Biological Studies, La Jolla, California 92037, United States
| | - Andrew T. Nelson
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Dan S. Tawfik
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Shina C.L. Kamerlin
- Department of Chemistry−BMC, Uppsala University, BMC Box 576, S-751 23 Uppsala, Sweden
| | - Joseph P. Noel
- Howard Hughes Medical Institute, Jack H. Skirball Center for Chemical Biology and Proteomics, The Salk Institute for Biological Studies, La Jolla, California 92037, United States
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12
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Maklashina E, Rajagukguk S, Iverson TM, Cecchini G. The unassembled flavoprotein subunits of human and bacterial complex II have impaired catalytic activity and generate only minor amounts of ROS. J Biol Chem 2018; 293:7754-7765. [PMID: 29610278 PMCID: PMC5961047 DOI: 10.1074/jbc.ra118.001977] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 03/28/2018] [Indexed: 01/28/2023] Open
Abstract
Complex II (SdhABCD) is a membrane-bound component of mitochondrial and bacterial electron transport chains, as well as of the TCA cycle. In this capacity, it catalyzes the reversible oxidation of succinate. SdhABCD contains the SDHA protein harboring a covalently bound FAD redox center and the iron-sulfur protein SDHB, containing three distinct iron-sulfur centers. When assembly of this complex is compromised, the flavoprotein SDHA may accumulate in the mitochondrial matrix or bacterial cytoplasm. Whether the unassembled SDHA has any catalytic activity, for example in succinate oxidation, fumarate reduction, reactive oxygen species (ROS) generation, or other off-pathway reactions, is not known. Therefore, here we investigated whether unassembled Escherichia coli SdhA flavoprotein, its homolog fumarate reductase (FrdA), and the human SDHA protein have succinate oxidase or fumarate reductase activity and can produce ROS. Using recombinant expression in E. coli, we found that the free flavoproteins from these divergent biological sources have inherently low catalytic activity and generate little ROS. These results suggest that the iron-sulfur protein SDHB in complex II is necessary for robust catalytic activity. Our findings are consistent with those reported for single-subunit flavoprotein homologs that are not associated with iron-sulfur or heme partner proteins.
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Affiliation(s)
- Elena Maklashina
- From the Molecular Biology Division, San Francisco Veterans Affairs Health Care System, San Francisco, California 94121, ,the Department of Biochemistry & Biophysics, University of California, San Francisco, California 94158, and
| | - Sany Rajagukguk
- From the Molecular Biology Division, San Francisco Veterans Affairs Health Care System, San Francisco, California 94121
| | - T. M. Iverson
- the Departments of Pharmacology and ,Biochemistry, ,the Center for Structural Biology, and ,the Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37232
| | - Gary Cecchini
- From the Molecular Biology Division, San Francisco Veterans Affairs Health Care System, San Francisco, California 94121, ,the Department of Biochemistry & Biophysics, University of California, San Francisco, California 94158, and , Recipient of Senior Research Career Scientist Award IK6BX004215 from the Department of Veterans Affairs. To whom correspondence should be addressed:
Molecular Biology Division (151-S), San Francisco Veterans Affairs Healthcare System, 4150 Clement St., San Francisco, CA 94121. Tel.:
415-221-4810, Ext. 24416; E-mail:
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13
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Starbird CA, Maklashina E, Sharma P, Qualls-Histed S, Cecchini G, Iverson TM. Structural and biochemical analyses reveal insights into covalent flavinylation of the Escherichia coli Complex II homolog quinol:fumarate reductase. J Biol Chem 2017; 292:12921-12933. [PMID: 28615448 DOI: 10.1074/jbc.m117.795120] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Revised: 06/07/2017] [Indexed: 11/06/2022] Open
Abstract
The Escherichia coli Complex II homolog quinol:fumarate reductase (QFR, FrdABCD) catalyzes the interconversion of fumarate and succinate at a covalently attached FAD within the FrdA subunit. The SdhE assembly factor enhances covalent flavinylation of Complex II homologs, but the mechanisms underlying the covalent attachment of FAD remain to be fully elucidated. Here, we explored the mechanisms of covalent flavinylation of the E. coli QFR FrdA subunit. Using a ΔsdhE E. coli strain, we show that the requirement for the assembly factor depends on the cellular redox environment. We next identified residues important for the covalent attachment and selected the FrdAE245 residue, which contributes to proton shuttling during fumarate reduction, for detailed biophysical and structural characterization. We found that QFR complexes containing FrdAE245Q have a structure similar to that of the WT flavoprotein, but lack detectable substrate binding and turnover. In the context of the isolated FrdA subunit, the anticipated assembly intermediate during covalent flavinylation, FrdAE245 variants had stability similar to that of WT FrdA, contained noncovalent FAD, and displayed a reduced capacity to interact with SdhE. However, small-angle X-ray scattering (SAXS) analysis of WT FrdA cross-linked to SdhE suggested that the FrdAE245 residue is unlikely to contribute directly to the FrdA-SdhE protein-protein interface. We also found that no auxiliary factor is absolutely required for flavinylation, indicating that the covalent flavinylation is autocatalytic. We propose that multiple factors, including the SdhE assembly factor and bound dicarboxylates, stimulate covalent flavinylation by preorganizing the active site to stabilize the quinone-methide intermediate.
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Affiliation(s)
- C A Starbird
- Graduate Program in Chemical and Physical Biology, Vanderbilt University, Nashville, Tennessee 37232
| | - Elena Maklashina
- Molecular Biology Division, Veterans Affairs Medical Center, San Francisco, California 94121; Department of Biochemistry and Biophysics, University of California, San Francisco, California 94158
| | - Pankaj Sharma
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232
| | - Susan Qualls-Histed
- Departments of Cell and Developmental Biology, Vanderbilt University, Nashville, Tennessee 37232
| | - Gary Cecchini
- Molecular Biology Division, Veterans Affairs Medical Center, San Francisco, California 94121; Department of Biochemistry and Biophysics, University of California, San Francisco, California 94158.
| | - T M Iverson
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232; Department of Biochemistry, Vanderbilt University, Nashville, Tennessee 37232; Center for Structural Biology, Vanderbilt University, Nashville, Tennessee 37232; Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee 37232.
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14
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Dunican BF, Hiller DA, Strobel SA. Transition State Charge Stabilization and Acid-Base Catalysis of mRNA Cleavage by the Endoribonuclease RelE. Biochemistry 2015; 54:7048-57. [PMID: 26535789 DOI: 10.1021/acs.biochem.5b00866] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The bacterial toxin RelE is a ribosome-dependent endoribonuclease. It is part of a type II toxin-antitoxin system that contributes to antibiotic resistance and biofilm formation. During amino acid starvation, RelE cleaves mRNA in the ribosomal A-site, globally inhibiting protein translation. RelE is structurally similar to microbial RNases that employ general acid-base catalysis to facilitate RNA cleavage. The RelE active site is atypical for acid-base catalysis, in that it is enriched with positively charged residues and lacks the prototypical histidine-glutamate catalytic pair, making the mechanism of mRNA cleavage unclear. In this study, we use a single-turnover kinetic analysis to measure the effect of pH and phosphorothioate substitution on the rate constant for cleavage of mRNA by wild-type RelE and seven active-site mutants. Mutation and thio effects indicate a major role for stabilization of increased negative change in the transition state by arginine 61. The wild-type RelE cleavage rate constant is pH-independent, but the reaction catalyzed by many of the mutants is strongly dependent on pH, suggestive of general acid-base catalysis. pH-rate curves indicate that wild-type RelE operates with the pK(a) of at least one catalytic residue significantly downshifted by the local environment. Mutation of any single active-site residue is sufficient to disrupt this microenvironment and revert the shifted pK(a) back above neutrality. pH-rate curves are consistent with K54 functioning as a general base and R81 as a general acid. The capacity of RelE to effect a large pK(a) shift and facilitate a common catalytic mechanism by uncommon means furthers our understanding of other atypical enzymatic active sites.
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Affiliation(s)
- Brian F Dunican
- Department of Molecular Biophysics and Biochemistry, Yale University , New Haven, Connecticut 06511, United States
| | - David A Hiller
- Department of Molecular Biophysics and Biochemistry, Yale University , New Haven, Connecticut 06511, United States
| | - Scott A Strobel
- Department of Molecular Biophysics and Biochemistry, Yale University , New Haven, Connecticut 06511, United States
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15
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Jongkon N, Chotpatiwetchkul W, Gleeson MP. Probing the Catalytic Mechanism Involved in the Isocitrate Lyase Superfamily: Hybrid Quantum Mechanical/Molecular Mechanical Calculations on 2,3-Dimethylmalate Lyase. J Phys Chem B 2015. [PMID: 26224328 DOI: 10.1021/acs.jpcb.5b04732] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The isocitrate lyase (ICL) superfamily catalyzes the cleavage of the C(2)-C(3) bond of various α-hydroxy acid substrates. Members of the family are found in bacteria, fungi, and plants and include ICL itself, oxaloacetate hydrolase (OAH), 2-methylisocitrate lyase (MICL), and (2R,3S)-dimethylmalate lyase (DMML) among others. ICL and related targets have been the focus of recent studies to treat bacterial and fungal infections, including tuberculosis. The catalytic process by which this family achieves C(2)-C(3) bond breaking is still not clear. Extensive structural studies have been performed on this family, leading to a number of plausible proposals for the catalytic mechanism. In this paper, we have applied quantum mechanical/molecular mechanical (QM/MM) methods to the most recently reported family member, DMML, to assess whether any of the mechanistic proposals offers a clear energetic advantage over the others. Our results suggest that Arg161 is the general base in the reaction and Cys124 is the general acid, giving rise to a rate-determining barrier of approximately 10 kcal/mol.
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Affiliation(s)
- Nathjanan Jongkon
- Department of Social and Applied Science, College of Industrial Technology, King Mongkut's University of Technology, North Bangkok , Bangkok 10800, Thailand
| | - Warot Chotpatiwetchkul
- Department of Chemistry, Faculty of Science, Kasetsart University , Chatuchak, Bangkok 10903, Thailand
| | - M Paul Gleeson
- Department of Chemistry, Faculty of Science, Kasetsart University , Chatuchak, Bangkok 10903, Thailand
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16
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Analysis of covalent flavinylation using thermostable succinate dehydrogenase from Thermus thermophilus and Sulfolobus tokodaii lacking SdhE homologs. FEBS Lett 2014; 588:1058-63. [PMID: 24566086 DOI: 10.1016/j.febslet.2014.02.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2013] [Revised: 02/05/2014] [Accepted: 02/05/2014] [Indexed: 11/20/2022]
Abstract
Recent studies have indicated that post-translational flavinylation of succinate dehydrogenase subunit A (SdhA) in eukaryotes and bacteria require the chaperone-like proteins Sdh5 and SdhE, respectively. How does covalent flavinylation occur in prokaryotes, which lack SdhE homologs? In this study, I showed that covalent flavinylation in two hyperthermophilic bacteria/archaea lacking SdhE, Thermus thermophilus and Sulfolobus tokodaii, requires heat and dicarboxylic acid. These thermophilic bacteria/archaea inhabit hot environments and are said to be genetically far removed from mesophilic bacteria which possess SdhE. Since mesophilic bacteria have been effective at covalent bonding in temperate environments, they may have caused the evolution of SdhE.
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17
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Hung JE, Fogle EJ, Garg N, Chekan JR, Nair SK, van der Donk WA. Chemical rescue and inhibition studies to determine the role of Arg301 in phosphite dehydrogenase. PLoS One 2014; 9:e87134. [PMID: 24498026 PMCID: PMC3909101 DOI: 10.1371/journal.pone.0087134] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Accepted: 12/19/2013] [Indexed: 12/11/2022] Open
Abstract
Phosphite dehydrogenase (PTDH) catalyzes the NAD(+)-dependent oxidation of phosphite to phosphate. This reaction requires the deprotonation of a water nucleophile for attack on phosphite. A crystal structure was recently solved that identified Arg301 as a potential base given its proximity and orientation to the substrates and a water molecule within the active site. Mutants of this residue showed its importance for efficient catalysis, with about a 100-fold loss in k cat and substantially increased K m,phosphite for the Ala mutant (R301A). The 2.35 Å resolution crystal structure of the R301A mutant with NAD(+) bound shows that removal of the guanidine group renders the active site solvent exposed, suggesting the possibility of chemical rescue of activity. We show that the catalytic activity of this mutant is restored to near wild-type levels by the addition of exogenous guanidinium analogues; Brønsted analysis of the rates of chemical rescue suggests that protonation of the rescue reagent is complete in the transition state of the rate-limiting step. Kinetic isotope effects on the reaction in the presence of rescue agents show that hydride transfer remains at least partially rate-limiting, and inhibition experiments show that K i of sulfite with R301A is ∼400-fold increased compared to the parent enzyme, similar to the increase in K m for phosphite in this mutant. The results of our experiments indicate that Arg301 plays an important role in phosphite binding as well as catalysis, but that it is not likely to act as an active site base.
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Affiliation(s)
- John E. Hung
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Emily J. Fogle
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Neha Garg
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Jonathan R. Chekan
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Satish K. Nair
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Wilfred A. van der Donk
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
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18
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Griffin MA, Davis JH, Strobel SA. Bacterial toxin RelE: a highly efficient ribonuclease with exquisite substrate specificity using atypical catalytic residues. Biochemistry 2013; 52:8633-42. [PMID: 24251350 DOI: 10.1021/bi401325c] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The toxin RelE is a ribosome-dependent endoribonuclease implicated in diverse cellular processes, including persistence. During amino acid starvation, RelE inhibits translation by cleaving ribosomal A-site mRNA. Although RelE is structurally similar to other microbial endoribonucleases, the active-site amino acid composition differs substantially and lacks obvious candidates for general acid-base functionality. Highly conserved RelE residues (Lys52, Lys54, Arg61, Arg81, and Tyr87) surround the mRNA scissile phosphate, and specific 16S rRNA contacts further contribute to substrate positioning. We used a single-turnover kinetic assay to evaluate the catalytic importance of individual residues in the RelE active site. Within the context of the ribosome, RelE rapidly cleaves A-site mRNA at a rate similar to those of traditional ribonucleases. Single-turnover rate constants decreased between 10(2)- and 10(6)-fold for the RelE active-site mutants of Lys52, Lys54, Arg61, and Arg81. RelE may principally promote catalysis via transition-state charge stabilization and leaving-group protonation, in addition to achieving in-line substrate positioning in cooperation with the ribosome. This kinetic analysis complements structural information to provide a foundation for understanding the molecular mechanism of this atypical endoribonuclease.
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Affiliation(s)
- Meghan A Griffin
- Department of Molecular Biophysics and Biochemistry, Yale University , New Haven, Connecticut 06511, United States
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19
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Shen H, Sun H, Li G. What is the role of motif D in the nucleotide incorporation catalyzed by the RNA-dependent RNA polymerase from poliovirus? PLoS Comput Biol 2012; 8:e1002851. [PMID: 23300428 PMCID: PMC3531290 DOI: 10.1371/journal.pcbi.1002851] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Accepted: 11/07/2012] [Indexed: 12/13/2022] Open
Abstract
Poliovirus (PV) is a well-characterized RNA virus, and the RNA-dependent RNA polymerase (RdRp) from PV (3Dpol) has been widely employed as an important model for understanding the structure-function relationships of RNA and DNA polymerases. Many experimental studies of the kinetics of nucleotide incorporation by RNA and DNA polymerases suggest that each nucleotide incorporation cycle basically consists of six sequential steps: (1) an incoming nucleotide binds to the polymerase-primer/template complex; (2) the ternary complex (nucleotide-polymerase-primer/template) undergoes a conformational change; (3) phosphoryl transfer occurs (the chemistry step); (4) a post-chemistry conformational change occurs; (5) pyrophosphate is released; (6) RNA or DNA translocation. Recently, the importance of structural motif D in nucleotide incorporation has been recognized, but the functions of motif D are less well explored so far. In this work, we used two computational techniques, molecular dynamics (MD) simulation and quantum mechanics (QM) method, to explore the roles of motif D in nucleotide incorporation catalyzed by PV 3Dpol. We discovered that the motif D, exhibiting high flexibility in either the presence or the absence of RNA primer/template, might facilitate the transportation of incoming nucleotide or outgoing pyrophosphate. We observed that the dynamic behavior of motif A, which should be essential to the polymerase function, was greatly affected by the motions of motif D. In the end, through QM calculations, we attempted to investigate the proton transfer in enzyme catalysis associated with a few amino acid residues of motifs F and D. The missing link between dynamics and structure or between dynamics and function of a protein has recently been paid much attention by many scientists since it has been recognized that a folded protein should be considered as an ensemble of conformations fluctuating in the neighborhood of its native state, instead of being pictured as a single static structure. Thus, to completely understand a protein and its functions, the dynamic features of the protein under a certain condition are required to be known. In this study, we performed atomistic MD simulations and QM calculations on the RNA-dependent RNA polymerase (RdRp) from poliovirus (PV), which is an important model system for gaining insight into the features of RNA and DNA polymerases. Through the computational studies of PV 3Dpol, we aim at finding out valuable information about the dynamic properties of the enzyme and exploring the molecular mechanism of the phosphoryl transfer in nucleotide incorporation.
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Affiliation(s)
- Hujun Shen
- Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
| | - Hui Sun
- Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
| | - Guohui Li
- Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China
- * E-mail:
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20
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Iverson TM. Catalytic mechanisms of complex II enzymes: a structural perspective. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1827:648-57. [PMID: 22995215 DOI: 10.1016/j.bbabio.2012.09.008] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 09/07/2012] [Accepted: 09/10/2012] [Indexed: 11/25/2022]
Abstract
Over a decade has passed since the elucidation of the first X-ray crystal structure of any complex II homolog. In the intervening time, the structures of five additional integral-membrane complex II enzymes and three homologs of the soluble domain have been determined. These structures have provided a framework for the analysis of enzymological studies of complex II superfamily enzymes, and have contributed to detailed proposals for reaction mechanisms at each of the two enzyme active sites, which catalyze dicarboxylate and quinone oxidoreduction, respectively. This review focuses on how structural data have augmented our understanding of catalysis by the superfamily. This article is part of a Special Issue entitled: Respiratory complex II: Role in cellular physiology and disease.
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Affiliation(s)
- T M Iverson
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232-6600, USA.
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21
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Hung JE, Fogle EJ, Christman HD, Johannes TW, Zhao H, Metcalf WW, van der Donk WA. Investigation of the role of Arg301 identified in the X-ray structure of phosphite dehydrogenase. Biochemistry 2012; 51:4254-62. [PMID: 22564138 PMCID: PMC3361975 DOI: 10.1021/bi201691w] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
![]()
Phosphite dehydrogenase (PTDH) from Pseudomonas
stutzeri catalyzes the nicotinamide adenine dinucleotide-dependent
oxidation
of phosphite to phosphate. The enzyme belongs to the family of d-hydroxy acid dehydrogenases (DHDHs). A search of the protein
databases uncovered many additional putative phosphite dehydrogenases.
The genes encoding four diverse candidates were cloned and expressed,
and the enzymes were purified and characterized. All oxidized phosphite
to phosphate and had similar kinetic parameters despite a low level
of pairwise sequence identity (39–72%). A recent crystal structure
identified Arg301 as a residue in the active site that has not been
investigated previously. Arg301 is fully conserved in the enzymes
shown here to be PTDHs, but the residue is not conserved in other
DHDHs. Kinetic analysis of site-directed mutants of this residue shows
that it is important for efficient catalysis, with an ∼100-fold
decrease in kcat and an almost 700-fold
increase in Km,phosphite for the R301A
mutant. Interestingly, the R301K mutant displayed a slightly higher kcat than the parent PTDH, and a more modest
increase in Km for phosphite (nearly 40-fold).
Given these results, Arg301 may be involved in the binding and orientation
of the phosphite substrate and/or play a catalytic role via electrostatic
interactions. Three other residues in the active site region that
are conserved in the PTDH orthologs but not DHDHs were identified
(Trp134, Tyr139, and Ser295). The importance of these residues was
also investigated by site-directed mutagenesis. All of the mutants
had kcat values similar to that of the
wild-type enzyme, indicating these residues are not important for
catalysis.
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Affiliation(s)
- John E Hung
- Department of Chemistry, University of Illinois, 600 South Mathews Avenue, Urbana, IL 61801, USA
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22
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Conley MP, Valero J, de Mendoza J. Guanidinium-Based Receptors for Oxoanions. Supramol Chem 2012. [DOI: 10.1002/9780470661345.smc061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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23
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Tomasiak TM, Archuleta TL, Andréll J, Luna-Chávez C, Davis TA, Sarwar M, Ham AJ, McDonald WH, Yankovskaya V, Stern HA, Johnston JN, Maklashina E, Cecchini G, Iverson TM. Geometric restraint drives on- and off-pathway catalysis by the Escherichia coli menaquinol:fumarate reductase. J Biol Chem 2010; 286:3047-56. [PMID: 21098488 DOI: 10.1074/jbc.m110.192849] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Complex II superfamily members catalyze the kinetically difficult interconversion of succinate and fumarate. Due to the relative simplicity of complex II substrates and their similarity to other biologically abundant small molecules, substrate specificity presents a challenge in this system. In order to identify determinants for on-pathway catalysis, off-pathway catalysis, and enzyme inhibition, crystal structures of Escherichia coli menaquinol:fumarate reductase (QFR), a complex II superfamily member, were determined bound to the substrate, fumarate, and the inhibitors oxaloacetate, glutarate, and 3-nitropropionate. Optical difference spectroscopy and computational modeling support a model where QFR twists the dicarboxylate, activating it for catalysis. Orientation of the C2-C3 double bond of activated fumarate parallel to the C(4a)-N5 bond of FAD allows orbital overlap between the substrate and the cofactor, priming the substrate for nucleophilic attack. Off-pathway catalysis, such as the conversion of malate to oxaloacetate or the activation of the toxin 3-nitropropionate may occur when inhibitors bind with a similarly activated bond in the same position. Conversely, inhibitors that do not orient an activatable bond in this manner, such as glutarate and citrate, are excluded from catalysis and act as inhibitors of substrate binding. These results support a model where electronic interactions via geometric constraint and orbital steering underlie catalysis by QFR.
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Affiliation(s)
- Thomas M Tomasiak
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
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24
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On the catalytic role of the active site residue E121 of E. coli l-aspartate oxidase. Biochimie 2010; 92:1335-42. [DOI: 10.1016/j.biochi.2010.06.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Accepted: 06/16/2010] [Indexed: 11/18/2022]
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25
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Paquete CM, Louro RO. Molecular details of multielectron transfer: the case of multiheme cytochromes from metal respiring organisms. Dalton Trans 2009; 39:4259-66. [PMID: 20422082 DOI: 10.1039/b917952f] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Shewanella are facultative anaerobic bacteria of remarkable respiratory versatility that includes the dissimilatory reduction of metal ores. They contain a large number of multiheme c-type cytochromes that play a significant role in various anaerobic respiratory processes. Of all the cytochromes found in Shewanella, only the two most abundant periplasmic cytochromes, the small tetraheme cytochrome (STC) and flavocytochrome c(3) (Fcc(3)) have been structurally characterized. For these two proteins the molecular bases for their redox properties were determined using spectroscopic methods based on paramagnetic NMR, that allow the contribution of specific hemes to be discriminated. In this perspective these results are reviewed in the context of the continuing effort to understand the molecular mechanisms of electron transfer in the respiratory chains of these organisms.
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26
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Bulfer SL, Scott EM, Couture JF, Pillus L, Trievel RC. Crystal structure and functional analysis of homocitrate synthase, an essential enzyme in lysine biosynthesis. J Biol Chem 2009; 284:35769-80. [PMID: 19776021 PMCID: PMC2791007 DOI: 10.1074/jbc.m109.046821] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2009] [Revised: 09/10/2009] [Indexed: 11/06/2022] Open
Abstract
Homocitrate synthase (HCS) catalyzes the first and committed step in lysine biosynthesis in many fungi and certain Archaea and is a potential target for antifungal drugs. Here we report the crystal structure of the HCS apoenzyme from Schizosaccharomyces pombe and two distinct structures of the enzyme in complex with the substrate 2-oxoglutarate (2-OG). The structures reveal that HCS forms an intertwined homodimer stabilized by domain-swapping between the N- and C-terminal domains of each monomer. The N-terminal catalytic domain is composed of a TIM barrel fold in which 2-OG binds via hydrogen bonds and coordination to the active site divalent metal ion, whereas the C-terminal domain is composed of mixed alpha/beta topology. In the structures of the HCS apoenzyme and one of the 2-OG binary complexes, a lid motif from the C-terminal domain occludes the entrance to the active site of the neighboring monomer, whereas in the second 2-OG complex the lid is disordered, suggesting that it regulates substrate access to the active site through its apparent flexibility. Mutations of the active site residues involved in 2-OG binding or implicated in acid-base catalysis impair or abolish activity in vitro and in vivo. Together, these results yield new insights into the structure and catalytic mechanism of HCSs and furnish a platform for developing HCS-selective inhibitors.
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Affiliation(s)
- Stacie L. Bulfer
- From the Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109 and
| | - Erin M. Scott
- the Division of Biological Sciences and UCSD Moores Cancer Center, University of California, San Diego, California 92093
| | - Jean-François Couture
- From the Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109 and
| | - Lorraine Pillus
- the Division of Biological Sciences and UCSD Moores Cancer Center, University of California, San Diego, California 92093
| | - Raymond C. Trievel
- From the Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109 and
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27
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Role of arginine in chemical cross-linking with N-hydroxysuccinimide esters. Anal Biochem 2009; 398:123-5. [PMID: 19931213 DOI: 10.1016/j.ab.2009.11.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2009] [Revised: 10/19/2009] [Accepted: 11/16/2009] [Indexed: 10/20/2022]
Abstract
In order to clarify whether arginine has a promoting effect on the acylation of hydroxyl groups of serine, threonine, or tyrosine by homobifunctional cross-linking agents in aqueous solution, we carried out systematic experiments with model peptides, comparing relative reaction yields with covalently protected and unprotected arginines by MALDI-MS. The guanidinium group could be demonstrated to contribute to the reactivity of hydroxyl groups toward N-hydroxysuccinimide esters and catalyze the nucleophilic substitution, probably via hydrogen bonds.
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28
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Pessanha M, Rothery EL, Miles CS, Reid GA, Chapman SK, Louro RO, Turner DL, Salgueiro CA, Xavier AV. Tuning of functional heme reduction potentials in Shewanella fumarate reductases. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:113-20. [DOI: 10.1016/j.bbabio.2008.11.007] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2008] [Revised: 11/06/2008] [Accepted: 11/07/2008] [Indexed: 11/15/2022]
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29
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Tomasiak TM, Maklashina E, Cecchini G, Iverson TM. A threonine on the active site loop controls transition state formation in Escherichia coli respiratory complex II. J Biol Chem 2008; 283:15460-8. [PMID: 18385138 PMCID: PMC2397489 DOI: 10.1074/jbc.m801372200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2008] [Revised: 03/26/2008] [Indexed: 11/06/2022] Open
Abstract
In Escherichia coli, the complex II superfamily members succinate:ubiquinone oxidoreductase (SQR) and quinol:fumarate reductase (QFR) participate in aerobic and anaerobic respiration, respectively. Complex II enzymes catalyze succinate and fumarate interconversion at the interface of two domains of the soluble flavoprotein subunit, the FAD binding domain and the capping domain. An 11-amino acid loop in the capping domain (Thr-A234 to Thr-A244 in quinol:fumarate reductase) begins at the interdomain hinge and covers the active site. Amino acids of this loop interact with both the substrate and a proton shuttle, potentially coordinating substrate binding and the proton shuttle protonation state. To assess the loop's role in catalysis, two threonine residues were mutated to alanine: QFR Thr-A244 (act-T; Thr-A254 in SQR), which hydrogen-bonds to the substrate at the active site, and QFR Thr-A234 (hinge-T; Thr-A244 in SQR), which is located at the hinge and hydrogen-bonds the proton shuttle. Both mutations impair catalysis and decrease substrate binding. The crystal structure of the hinge-T mutation reveals a reorientation between the FAD-binding and capping domains that accompanies proton shuttle alteration. Taken together, hydrogen bonding from act-T to substrate may coordinate with interdomain motions to twist the double bond of fumarate and introduce the strain important for attaining the transition state.
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Affiliation(s)
- Thomas M. Tomasiak
- Departments of Pharmacology and Biochemistry, Vanderbilt University, Nashville, Tennessee 37232, the Molecular Biology Division, Veterans Affairs Medical Center, San Francisco, California 94121, and the Department of Biochemistry and Biophysics, University of California, San Francisco, California 94158
| | - Elena Maklashina
- Departments of Pharmacology and Biochemistry, Vanderbilt University, Nashville, Tennessee 37232, the Molecular Biology Division, Veterans Affairs Medical Center, San Francisco, California 94121, and the Department of Biochemistry and Biophysics, University of California, San Francisco, California 94158
| | - Gary Cecchini
- Departments of Pharmacology and Biochemistry, Vanderbilt University, Nashville, Tennessee 37232, the Molecular Biology Division, Veterans Affairs Medical Center, San Francisco, California 94121, and the Department of Biochemistry and Biophysics, University of California, San Francisco, California 94158
| | - Tina M. Iverson
- Departments of Pharmacology and Biochemistry, Vanderbilt University, Nashville, Tennessee 37232, the Molecular Biology Division, Veterans Affairs Medical Center, San Francisco, California 94121, and the Department of Biochemistry and Biophysics, University of California, San Francisco, California 94158
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30
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van der Kamp MW, Perruccio F, Mulholland AJ. High-level QM/MM modelling predicts an arginine as the acid in the condensation reaction catalysed by citrate synthase. Chem Commun (Camb) 2008:1874-6. [PMID: 18401503 DOI: 10.1039/b800496j] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
High-level ab initio quantum mechanical/molecular mechanical (QM/MM) modelling of citryl-CoA formation in citrate synthase reveals that an arginine residue acts as the proton donor; this proposed new mechanism helps to explain how chemical and large scale conformational changes are coupled in this paradigmatic enzyme.
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Affiliation(s)
- Marc W van der Kamp
- Centre for Computational Chemistry, School of Chemistry, University of Bristol, Cantocks Close, Bristol, UK
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31
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3-Keto-5α-steroid Δ1-dehydrogenase from Rhodococcus erythropolis SQ1 and its orthologue in Mycobacterium tuberculosis H37Rv are highly specific enzymes that function in cholesterol catabolism. Biochem J 2008; 410:339-46. [DOI: 10.1042/bj20071130] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The Rhodococcus erythropolis SQ1 kstD3 gene was cloned, heterologously expressed and biochemically characterized as a KSTD3 (3-keto-5α-steroid Δ1-dehydrogenase). Upstream of kstD3, an ORF (open reading frame) with similarity to Δ4 KSTD (3-keto-5α-steroid Δ4-dehydrogenase) was found, tentatively designated kst4D. Biochemical analysis revealed that the Δ1 KSTD3 has a clear preference for 3-ketosteroids with a saturated A-ring, displaying highest activity on 5α-AD (5α-androstane-3,17-dione) and 5α-T (5α-testosterone; also known as 17β-hydroxy-5α-androstane-3-one). The KSTD1 and KSTD2 enzymes, on the other hand, clearly prefer (9α-hydroxy-)4-androstene-3,17-dione as substrates. Phylogenetic analysis of known and putative KSTD amino acid sequences showed that the R. erythropolis KSTD proteins cluster into four distinct groups. Interestingly, Δ1 KSTD3 from R. erythropolis SQ1 clustered with Rv3537, the only Δ1 KSTD present in Mycobacterium tuberculosis H37Rv, a protein involved in cholesterol catabolism and pathogenicity. The substrate range of heterologously expressed Rv3537 enzyme was nearly identical with that of Δ1 KSTD3, indicating that these are orthologous enzymes. The results imply that 5α-AD and 5α-T are newly identified intermediates in the cholesterol catabolic pathway, and important steroids with respect to pathogenicity.
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32
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You YO, van der Donk WA. Mechanistic investigations of the dehydration reaction of lacticin 481 synthetase using site-directed mutagenesis. Biochemistry 2007; 46:5991-6000. [PMID: 17455908 PMCID: PMC2517115 DOI: 10.1021/bi602663x] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Lantibiotic synthetases catalyze the dehydration of Ser and Thr residues in their peptide substrates to dehydroalanine (Dha) and dehydrobutyrine (Dhb), respectively, followed by the conjugate addition of Cys residues to the Dha and Dhb residues to generate the thioether cross-links lanthionine and methyllanthionine, respectively. In this study ten conserved residues were mutated in the dehydratase domain of the best characterized family member, lacticin 481 synthetase (LctM). Mutation of His244 and Tyr408 did not affect dehydration activity with the LctA substrate whereas mutation of Asn247, Glu261, and Glu446 considerably slowed down dehydration and resulted in incomplete conversion. Mutation of Lys159 slowed down both steps of the net dehydration: phosphorylation of Ser/Thr residues and the subsequent phosphate elimination step to form the dehydro amino acids. Mutation of Arg399 to Met or Leu resulted in mutants that had phosphorylation activity but displayed greatly decreased phosphate elimination activity. The Arg399Lys mutant retained both activities, however. Similarly, the Thr405Ala mutant phosphorylated the LctA substrate but had compromised elimination activity. Finally, mutation of Asp242 or Asp259 to Asn led to mutant enzymes that lacked detectable dehydration activity. Whereas the Asp242Asn mutant retained phosphate elimination activity, the Asp259Asn mutant was not able to eliminate phosphate from a phosphorylated substrate peptide. A model is presented that accounts for the observed phenotypes of these mutant enzymes.
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Affiliation(s)
- Young Ok You
- Department of Biochemistry, University of Illinois at Urbana-Champaign, 600 S. Mathews Ave, Urbana, Illinois, telephone (217) 244 5360, FAX (217) 244 8533
| | - Wilfred A. van der Donk
- Department of Biochemistry, University of Illinois at Urbana-Champaign, 600 S. Mathews Ave, Urbana, Illinois, telephone (217) 244 5360, FAX (217) 244 8533
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 S. Mathews Ave, Urbana, Illinois, telephone (217) 244 5360, FAX (217) 244 8533
- To whom correspondence should be addressed. Phone: (217) 244-5360 FAX (217) 244 8024 E-mail:
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33
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Affiliation(s)
- James P McEvoy
- Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, USA
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34
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Blondeau P, Segura M, Pérez-Fernández R, de Mendoza J. Molecular recognition of oxoanions based on guanidinium receptors. Chem Soc Rev 2006; 36:198-210. [PMID: 17264923 DOI: 10.1039/b603089k] [Citation(s) in RCA: 306] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Guanidinium is a versatile functional group with unique properties. In biological systems, hydrogen-bonding and electrostatic interactions involving the arginine side chains of proteins are critical to stabilise complexes between proteins and nucleic acids, carbohydrates or other proteins. Leading examples of artificial receptors for carboxylates, phosphates and other oxoanions, such as sulfate or nitrate are highlighted in this tutorial review, addressed to readers interested in biology, chemistry and supramolecular chemistry.
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Affiliation(s)
- Pascal Blondeau
- Institute of Chemical Research of Catalonia (ICIQ), 43007 Tarragona, Spain
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35
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Narváez AJ, Voevodskaya N, Thelander L, Gräslund A. The Involvement of Arg265 of Mouse Ribonucleotide Reductase R2 Protein in Proton Transfer and Catalysis. J Biol Chem 2006; 281:26022-8. [PMID: 16829694 DOI: 10.1074/jbc.m604598200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ribonucleotide reductase class I enzymes consist of two non-identical subunits, R1 and R2, the latter containing a diiron carboxylate center and a stable tyrosyl radical (Tyr*), both essential for catalysis. Catalysis is known to involve highly conserved amino acid residues covering a range of approximately 35 A and a concerted mechanism involving long range electron transfer, probably coupled to proton transfer. A number of residues involved in electron transfer in both the R1 and R2 proteins have been identified, but no direct model has been presented regarding the proton transfer side of the process. Arg265 is conserved in all known sequences of class Ia R2. In this study we have used site-directed mutagenesis to gain insight into the role of this residue, which lies close to the catalytically essential Asp266 and Trp103. Mutants to Arg265 included replacement by Ala, Glu, Gln, and Tyr. All mutants of Arg265 were found to have no or low catalytic activity with the exception of Arg265 to Glu, which shows approximately 40% of the activity of native R2. We also found that the Arg mutants were capable of stable tyrosyl radical generation, with similar kinetics of radical formation and R1 binding as native R2. Our results, supported by molecular modeling, strongly suggest that Arg265 is involved in the proton-coupled electron transfer pathway and may act as a proton mediator during catalysis.
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Affiliation(s)
- Ana J Narváez
- Department of Biochemistry and Biophysics, Stockholm University, SE-10691 Stockholm, Sweden
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36
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Pankhurst KL, Mowat CG, Rothery EL, Hudson JM, Jones AK, Miles CS, Walkinshaw MD, Armstrong FA, Reid GA, Chapman SK. A proton delivery pathway in the soluble fumarate reductase from Shewanella frigidimarina. J Biol Chem 2006; 281:20589-97. [PMID: 16699170 DOI: 10.1074/jbc.m603077200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mechanism for fumarate reduction by the soluble fumarate reductase from Shewanella frigidimarina involves hydride transfer from FAD and proton transfer from the active-site acid, Arg-402. It has been proposed that Arg-402 forms part of a proton transfer pathway that also involves Glu-378 and Arg-381 but, unusually, does not involve any bound water molecules. To gain further insight into the importance of this proton pathway we have perturbed it by substituting Arg-381 by lysine and methionine and Glu-378 by aspartate. Although all the mutant enzymes retain measurable activities, there are orders-of-magnitude decreases in their k(cat) values compared with the wild-type enzyme. Solvent kinetic isotope effects show that proton transfer is rate-limiting in the wild-type and mutant enzymes. Proton inventories indicate that the proton pathway involves multiple exchangeable groups. Fast scan protein-film voltammetric studies on wild-type and R381K enzymes show that the proton transfer pathway delivers one proton per catalytic cycle and is not required for transporting the other proton, which transfers as a hydride from the reduced, protonated FAD. The crystal structures of E378D and R381M mutant enzymes have been determined to 1.7 and 2.1 A resolution, respectively. They allow an examination of the structural changes that disturb proton transport. Taken together, the results indicate that Arg-381, Glu-378, and Arg-402 form a proton pathway that is completely conserved throughout the fumarate reductase/succinate dehydrogenase family of enzymes.
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Affiliation(s)
- Katherine L Pankhurst
- Edinburgh and St. Andrews Research School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, UK
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37
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Lucas MF, Ramos MJ. Mechanism of a Soluble Fumarate Reductase from Shewanella frigidimarina: A Theoretical Study. J Phys Chem B 2006; 110:10550-6. [PMID: 16722766 DOI: 10.1021/jp057456t] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The mechanism of a unique fumarate reductase is explored using the hybrid density functional B3LYP method. The calculations show a two-step mechanism, initiated with a hydride transfer from FAD (flavin adenine dinucleotide) to fumarate, followed by a proton shift from Arg402. The rate-limiting process is assigned to the hydride transfer, and the energetics are consistent with experimental data. It is shown that the enzyme is essential to correctly position the substrate in the active site, stabilizing its extremely anionic character.
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Affiliation(s)
- M Fatima Lucas
- REQUIMTE, Departamento de Química, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal
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38
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Maklashina E, Iverson TM, Sher Y, Kotlyar V, Andréll J, Mirza O, Hudson JM, Armstrong FA, Rothery RA, Weiner JH, Cecchini G. Fumarate Reductase and Succinate Oxidase Activity of Escherichia coli Complex II Homologs Are Perturbed Differently by Mutation of the Flavin Binding Domain. J Biol Chem 2006; 281:11357-65. [PMID: 16484232 DOI: 10.1074/jbc.m512544200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Escherichia coli complex II homologues succinate:ubiquinone oxidoreductase (SQR, SdhCDAB) and menaquinol:fumarate oxidoreductase (QFR, FrdABCD) have remarkable structural homology at their dicarboxylate binding sites. Although both SQR and QFR can catalyze the interconversion of fumarate and succinate, QFR is a much better fumarate reductase, and SQR is a better succinate oxidase. An exception to the conservation of amino acids near the dicarboxylate binding sites of the two enzymes is that there is a Glu (FrdA Glu-49) near the covalently bound FAD cofactor in most QFRs, which is replaced with a Gln (SdhA Gln-50) in SQRs. The role of the amino acid side chain in enzymes with Glu/Gln/Ala substitutions at FrdA Glu-49 and SdhA Gln-50 has been investigated in this study. The data demonstrate that the mutant enzymes with Ala substitutions in either QFR or SQR remain functionally similar to their wild type counterparts. There were, however, dramatic changes in the catalytic properties when Glu and Gln were exchanged for each other in QFR and SQR. The data show that QFR and SQR enzymes are more efficient succinate oxidases when Gln is in the target position and a better fumarate reductase when Glu is present. Overall, structural and catalytic analyses of the FrdA E49Q and SdhA Q50E mutants suggest that coulombic effects and the electronic state of the FAD are critical in dictating the preferred directionality of the succinate/fumarate interconversions catalyzed by the complex II superfamily.
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Affiliation(s)
- Elena Maklashina
- Molecular Biology Division, Veterans Affairs Medical Center, San Francisco, California 94121, USA
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39
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Wardrope C, Mowat CG, Walkinshaw MD, Reid GA, Chapman SK. Fumarate reductase: structural and mechanistic insights from the catalytic reduction of 2-methylfumarate. FEBS Lett 2006; 580:1677-80. [PMID: 16497301 DOI: 10.1016/j.febslet.2006.02.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2005] [Revised: 01/19/2006] [Accepted: 02/09/2006] [Indexed: 10/25/2022]
Abstract
The soluble fumarate reductase (FR) from Shewanella frigidimarina can catalyse the reduction of 2-methylfumarate with a k(cat) of 9.0 s(-1) and a K(M) of 32 microM. This produces the chiral molecule 2-methylsuccinate. Here, we present the structure of FR to a resolution of 1.5 A with 2-methylfumarate bound at the active site. The mode of binding of 2-methylfumarate allows us to predict the stereochemistry of the product as (S)-2-methylsuccinate. To test this prediction we have analysed the product stereochemistry by circular dichroism spectroscopy and confirmed the production of (S)-2-methylsuccinate.
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Affiliation(s)
- Caroline Wardrope
- EaStCHEM, School of Chemistry, University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, UK
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40
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Guillén Schlippe YV, Hedstrom L. A twisted base? The role of arginine in enzyme-catalyzed proton abstractions. Arch Biochem Biophys 2005; 433:266-78. [PMID: 15581582 DOI: 10.1016/j.abb.2004.09.018] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2004] [Revised: 09/13/2004] [Indexed: 10/26/2022]
Abstract
Arginine residues are generally considered poor candidates for the role of general bases because they are predominantly protonated at physiological pH. Nonetheless, Arg residues have recently emerged as general bases in several enzymes: IMP dehydrogenase, pectate/pectin lyases, fumarate reductase, and l-aspartate oxidase. The experimental evidence suggesting this mechanistic function is reviewed. Although these enzymes have several different folds and distinct evolutionary origins, a common structural motif is found where the critical Arg residue is solvent accessible and adjacent to carboxylate groups. The chemistry of the guanidine group suggests unique strategies to lower the pK(a) of Arg. Lastly, the presumption that general bases must be predominantly deprotonated is revisited.
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41
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McEvoy JP, Gascon JA, Batista VS, Brudvig GW. The mechanism of photosynthetic water splitting. Photochem Photobiol Sci 2005; 4:940-9. [PMID: 16307106 DOI: 10.1039/b506755c] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Oxygenic photosynthesis, which provides the biosphere with most of its chemical energy, uses water as its source of electrons. Water is photochemically oxidized by the protein complex photosystem II (PSII), which is found, along with other proteins of the photosynthetic light reactions, in the thylakoid membranes of cyanobacteria and of green plant chloroplasts. Water splitting is catalyzed by the oxygen-evolving complex (OEC) of PSII, producing dioxygen gas, protons and electrons. O(2) is released into the atmosphere, sustaining all aerobic life on earth; product protons are released into the thylakoid lumen, augmenting a proton concentration gradient across the membrane; and photo-energized electrons pass to the rest of the electron-transfer pathway. The OEC contains four manganese ions, one calcium ion and (almost certainly) a chloride ion, but its precise structure and catalytic mechanism remain unclear. In this paper, we develop a chemically complete structure of the OEC and its environment by using molecular mechanics calculations to extend and slightly adjust the recently-obtained X-ray crystallographic model with reference to this structure and to some important recent experimental results.
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Affiliation(s)
- James P McEvoy
- Department of Chemistry, Yale University, PO Box 208107, New Haven, CT 06520-8107, USA
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42
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Girvan HM, Marshall KR, Lawson RJ, Leys D, Joyce MG, Clarkson J, Smith WE, Cheesman MR, Munro AW. Flavocytochrome P450 BM3 Mutant A264E Undergoes Substrate-dependent Formation of a Novel Heme Iron Ligand Set. J Biol Chem 2004; 279:23274-86. [PMID: 15020591 DOI: 10.1074/jbc.m401716200] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A conserved glutamate covalently attaches the heme to the protein backbone of eukaryotic CYP4 P450 enzymes. In the related Bacillus megaterium P450 BM3, the corresponding residue is Ala264. The A264E mutant was generated and characterized by kinetic and spectroscopic methods. A264E has an altered absorption spectrum compared with the wild-type enzyme (Soret maximum at approximately 420.5 nm). Fatty acid substrates produced an inhibitor-like spectral change, with the Soret band shifting to 426 nm. Optical titrations with long-chain fatty acids indicated higher affinity for A264E over the wild-type enzyme. The heme iron midpoint reduction potential in substrate-free A264E is more positive than that in wild-type P450 BM3 and was not changed upon substrate binding. EPR, resonance Raman, and magnetic CD spectroscopies indicated that A264E remains in the low-spin state upon substrate binding, unlike wild-type P450 BM3. EPR spectroscopy showed two major species in substrate-free A264E. The first has normal Cys-aqua iron ligation. The second resembles formate-ligated P450cam. Saturation with fatty acid increased the population of the latter species, suggesting that substrate forces on the glutamate to promote a Cys-Glu ligand set, present in lower amounts in the substrate-free enzyme. A novel charge-transfer transition in the near-infrared magnetic CD spectrum provides a spectroscopic signature characteristic of the new A264E heme iron ligation state. A264E retains oxygenase activity, despite glutamate coordination of the iron, indicating that structural rearrangements occur following heme iron reduction to allow dioxygen binding. Glutamate coordination of the heme iron is confirmed by structural studies of the A264E mutant (Joyce, M. G., Girvan, H. M., Munro, A. W., and Leys, D. (2004) J. Biol. Chem. 279, 23287-23293).
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Affiliation(s)
- Hazel M Girvan
- Department of Biochemistry, University of Leicester, Leicester LE1 7RH, United Kingdom
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43
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McEvoy JP, Brudvig GW. Structure-based mechanism of photosynthetic water oxidation. Phys Chem Chem Phys 2004. [DOI: 10.1039/b407500e] [Citation(s) in RCA: 174] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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