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Smith MM, Moran GR. Building on a theme: The redox hierarchy of pyridine nucleotide-disulfide oxidoreductases. Arch Biochem Biophys 2024; 755:109966. [PMID: 38537870 DOI: 10.1016/j.abb.2024.109966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Revised: 03/14/2024] [Accepted: 03/21/2024] [Indexed: 04/24/2024]
Abstract
Flavin disulfide reductases (FDRs) are FAD-dependent enzymes that transmit electrons from NAD(P)H to reduce specific oxidant substrate disulfides. These enzymes have been studied extensively, most particularly the paradigm examples: glutathione reductase and thioredoxin reductase. The common, though not universal, traits of the family include a tyrosine- or phenylalanine-gated binding pocket for NAD(P) nicotinamides adjacent to the FAD isoalloxazine re-face, and a disulfide stacked against the si-face of the isoalloxazine whose dithiol form is activated for subsequent exchange reactions by a nearby histidine acting as a base. This arrangement promotes transduction of the reducing equivalents for disulfide exchange relay reactions. From an observational standpoint the proximal parallel stacking of three redox moieties induces up to three opportunities for unique charge transfer interactions (NAD(P)H FAD, NAD(P)+•FADH2, and FAD•thiolate). In transient state, the charge transfer transitions provide discrete signals to assign reaction sequences. This review summarizes the lineage of observations for the FDR enzymes that have been extensively studied. Where applicable and in order to chart a consistent interpretation of the record, only data derived from studies that used anaerobic methods are cited. These data reveal a recurring theme for catalysis that is elaborated with specific additional functionalities for each oxidant substrate.
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Affiliation(s)
- Madison M Smith
- Department of Chemistry and Biochemistry, 1068 W Sheridan Rd, Loyola University Chicago, Chicago, IL, 60660, United States
| | - Graham R Moran
- Department of Chemistry and Biochemistry, 1068 W Sheridan Rd, Loyola University Chicago, Chicago, IL, 60660, United States.
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2
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Skalidis I, Kyrilis FL, Tüting C, Hamdi F, Träger TK, Belapure J, Hause G, Fratini M, O'Reilly FJ, Heilmann I, Rappsilber J, Kastritis PL. Structural analysis of an endogenous 4-megadalton succinyl-CoA-generating metabolon. Commun Biol 2023; 6:552. [PMID: 37217784 DOI: 10.1038/s42003-023-04885-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Accepted: 04/27/2023] [Indexed: 05/24/2023] Open
Abstract
The oxoglutarate dehydrogenase complex (OGDHc) participates in the tricarboxylic acid cycle and, in a multi-step reaction, decarboxylates α-ketoglutarate, transfers succinyl to CoA, and reduces NAD+. Due to its pivotal role in metabolism, OGDHc enzymatic components have been studied in isolation; however, their interactions within the endogenous OGDHc remain elusive. Here, we discern the organization of a thermophilic, eukaryotic, native OGDHc in its active state. By combining biochemical, biophysical, and bioinformatic methods, we resolve its composition, 3D architecture, and molecular function at 3.35 Å resolution. We further report the high-resolution cryo-EM structure of the OGDHc core (E2o), which displays various structural adaptations. These include hydrogen bonding patterns confining interactions of OGDHc participating enzymes (E1o-E2o-E3), electrostatic tunneling that drives inter-subunit communication, and the presence of a flexible subunit (E3BPo), connecting E2o and E3. This multi-scale analysis of a succinyl-CoA-producing native cell extract provides a blueprint for structure-function studies of complex mixtures of medical and biotechnological value.
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Affiliation(s)
- Ioannis Skalidis
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, 06120, Halle/Saale, Germany
- Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3, 06120, Halle/Saale, Germany
| | - Fotis L Kyrilis
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, 06120, Halle/Saale, Germany
- Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3, 06120, Halle/Saale, Germany
| | - Christian Tüting
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, 06120, Halle/Saale, Germany
| | - Farzad Hamdi
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, 06120, Halle/Saale, Germany
| | - Toni K Träger
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, 06120, Halle/Saale, Germany
- Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3, 06120, Halle/Saale, Germany
| | - Jaydeep Belapure
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, 06120, Halle/Saale, Germany
| | - Gerd Hause
- Biozentrum, Martin Luther University Halle-Wittenberg, Weinbergweg 22, 06120, Halle/Saale, Germany
| | - Marta Fratini
- Department of Plant Biochemistry, Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Str. 3a, 06120, Halle/Saale, Germany
| | - Francis J O'Reilly
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute (NCI), Frederick, MD, 21702-1201, USA
| | - Ingo Heilmann
- Department of Plant Biochemistry, Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Str. 3a, 06120, Halle/Saale, Germany
| | - Juri Rappsilber
- Bioanalytics, Institute of Biotechnology, Technische Universität Berlin, 13355, Berlin, Germany
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3BF, Scotland, United Kingdom
| | - Panagiotis L Kastritis
- Interdisciplinary Research Center HALOmem, Charles Tanford Protein Center, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3a, 06120, Halle/Saale, Germany.
- Institute of Biochemistry and Biotechnology, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3, 06120, Halle/Saale, Germany.
- Biozentrum, Martin Luther University Halle-Wittenberg, Weinbergweg 22, 06120, Halle/Saale, Germany.
- Institute of Chemical Biology, National Hellenic Research Foundation, Athens, 11635, Greece.
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3
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Heyes DJ, Lakavath B, Hardman SJO, Sakuma M, Hedison TM, Scrutton NS. Photochemical Mechanism of Light-Driven Fatty Acid Photodecarboxylase. ACS Catal 2020; 10:6691-6696. [PMID: 32905273 PMCID: PMC7469136 DOI: 10.1021/acscatal.0c01684] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 05/18/2020] [Indexed: 01/06/2023]
Abstract
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Fatty
acid photodecarboxylase (FAP) is a promising target for the
production of biofuels and fine chemicals. It contains a flavin adenine
dinucleotide cofactor and catalyzes the blue-light-dependent decarboxylation
of fatty acids to generate the corresponding alkane. However, little
is known about the catalytic mechanism of FAP, or how light is used
to drive enzymatic decarboxylation. Here, we have used a combination
of time-resolved and cryogenic trapping UV–visible absorption
spectroscopy to characterize a red-shifted flavin intermediate observed
in the catalytic cycle of FAP. We show that this intermediate can
form below the “glass transition” temperature of proteins,
whereas the subsequent decay of the species proceeds only at higher
temperatures, implying a role for protein motions in the decay of
the intermediate. Solvent isotope effect measurements, combined with
analyses of selected site-directed variants of FAP, suggest that the
formation of the red-shifted flavin species is directly coupled with
hydrogen atom transfer from a nearby active site cysteine residue,
yielding the final alkane product. Our study suggests that this cysteine
residue forms a thiolate-flavin charge-transfer species, which is
assigned as the red-shifted flavin intermediate. Taken together, our
data provide insights into light-dependent decarboxylase mechanisms
catalyzed by FAP and highlight important considerations in the (re)design
of flavin-based photoenzymes.
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Affiliation(s)
- Derren J. Heyes
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K
| | - Balaji Lakavath
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K
| | - Samantha J. O. Hardman
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K
| | - Michiyo Sakuma
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K
| | - Tobias M. Hedison
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K
| | - Nigel S. Scrutton
- Manchester Institute of Biotechnology, University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K
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Moxley MA, Beard DA, Bazil JN. Global Kinetic Analysis of Mammalian E3 Reveals pH-dependent NAD+/NADH Regulation, Physiological Kinetic Reversibility, and Catalytic Optimum. J Biol Chem 2015; 291:2712-30. [PMID: 26644471 DOI: 10.1074/jbc.m115.676619] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Indexed: 12/11/2022] Open
Abstract
Mammalian E3 is an essential mitochondrial enzyme responsible for catalyzing the terminal reaction in the oxidative catabolism of several metabolites. E3 is a key regulator of metabolic fuel selection as a component of the pyruvate dehydrogenase complex (PDHc). E3 regulates PDHc activity by altering the affinity of pyruvate dehydrogenase kinase, an inhibitor of the enzyme complex, through changes in reduction and acetylation state of lipoamide moieties set by the NAD(+)/NADH ratio. Thus, an accurate kinetic model of E3 is needed to predict overall mammalian PDHc activity. Here, we have combined numerous literature data sets and new equilibrium spectroscopic experiments with a multitude of independently collected forward and reverse steady-state kinetic assays using pig heart E3. The latter kinetic assays demonstrate a pH-dependent transition of NAD(+) activation to inhibition, shown here, to our knowledge, for the first time in a single consistent data set. Experimental data were analyzed to yield a thermodynamically constrained four-redox-state model of E3 that simulates pH-dependent activation/inhibition and active site redox states for various conditions. The developed model was used to determine substrate/product conditions that give maximal E3 rates and show that, due to non-Michaelis-Menten behavior, the maximal flux is different compared with the classically defined kcat.
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Affiliation(s)
- Michael A Moxley
- From the Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan 48109
| | - Daniel A Beard
- From the Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan 48109
| | - Jason N Bazil
- From the Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan 48109
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6
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Moxley MA, Beard DA, Bazil JN. A pH-dependent kinetic model of dihydrolipoamide dehydrogenase from multiple organisms. Biophys J 2014; 107:2993-3007. [PMID: 25517164 PMCID: PMC4269776 DOI: 10.1016/j.bpj.2014.09.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Revised: 09/19/2014] [Accepted: 09/24/2014] [Indexed: 11/18/2022] Open
Abstract
Dihydrolipoamide dehydrogenase is a flavoenzyme that reversibly catalyzes the oxidation of reduced lipoyl substrates with the reduction of NAD(+) to NADH. In vivo, the dihydrolipoamide dehydrogenase component (E3) is associated with the pyruvate, α-ketoglutarate, and glycine dehydrogenase complexes. The pyruvate dehydrogenase (PDH) complex connects the glycolytic flux to the tricarboxylic acid cycle and is central to the regulation of primary metabolism. Regulation of PDH via regulation of the E3 component by the NAD(+)/NADH ratio represents one of the important physiological control mechanisms of PDH activity. Furthermore, previous experiments with the isolated E3 component have demonstrated the importance of pH in dictating NAD(+)/NADH ratio effects on enzymatic activity. Here, we show that a three-state mechanism that represents the major redox states of the enzyme and includes a detailed representation of the active-site chemistry constrained by both equilibrium and thermodynamic loop constraints can be used to model regulatory NAD(+)/NADH ratio and pH effects demonstrated in progress-curve and initial-velocity data sets from rat, human, Escherichia coli, and spinach enzymes. Global fitting of the model provides stable predictions to the steady-state distributions of enzyme redox states as a function of lipoamide/dihydrolipoamide, NAD(+)/NADH, and pH. These distributions were calculated using physiological NAD(+)/NADH ratios representative of the diverse organismal sources of E3 analyzed in this study. This mechanistically detailed, thermodynamically constrained, pH-dependent model of E3 provides a stable platform on which to accurately model multicomponent enzyme complexes that implement E3 from a variety of organisms.
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Affiliation(s)
- Michael A Moxley
- Department of Biochemistry, Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - Daniel A Beard
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan.
| | - Jason N Bazil
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan
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7
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Angelucci F, Dimastrogiovanni D, Boumis G, Brunori M, Miele AE, Saccoccia F, Bellelli A. Mapping the catalytic cycle of Schistosoma mansoni thioredoxin glutathione reductase by X-ray crystallography. J Biol Chem 2010; 285:32557-67. [PMID: 20659890 PMCID: PMC2952258 DOI: 10.1074/jbc.m110.141960] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2010] [Revised: 07/08/2010] [Indexed: 11/06/2022] Open
Abstract
Schistosomiasis is the second most widespread human parasitic disease. It is principally treated with one drug, praziquantel, that is administered to 100 million people each year; less sensitive strains of schistosomes are emerging. One of the most appealing drug targets against schistosomiasis is thioredoxin glutathione reductase (TGR). This natural chimeric enzyme is a peculiar fusion of a glutaredoxin domain with a thioredoxin selenocysteine (U)-containing reductase domain. Selenocysteine is located on a flexible C-terminal arm that is usually disordered in the available structures of the protein and is essential for the full catalytic activity of TGR. In this study, we dissect the catalytic cycle of Schistosoma mansoni TGR by structural and functional analysis of the U597C mutant. The crystallographic data presented herein include the following: the oxidized form (at 1.9 Å resolution); the NADPH- and GSH-bound forms (2.3 and 1.9 Å, respectively); and a different crystal form of the (partially) reduced enzyme (3.1 Å), showing the physiological dimer and the entire C terminus of one subunit. Whenever possible, we determined the rate constants for the interconversion between the different oxidation states of TGR by kinetic methods. By combining the crystallographic analysis with computer modeling, we were able to throw further light on the mechanism of action of S. mansoni TGR. In particular, we hereby propose the putative functionally relevant conformational change of the C terminus after the transfer of reducing equivalents from NADPH to the redox sites of the enzyme.
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Affiliation(s)
- Francesco Angelucci
- From the Department of Biochemical Sciences “A. Rossi Fanelli,” CNR Institute of Molecular Biology and Pathology and Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy
| | - Daniela Dimastrogiovanni
- From the Department of Biochemical Sciences “A. Rossi Fanelli,” CNR Institute of Molecular Biology and Pathology and Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy
| | - Giovanna Boumis
- From the Department of Biochemical Sciences “A. Rossi Fanelli,” CNR Institute of Molecular Biology and Pathology and Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy
| | - Maurizio Brunori
- From the Department of Biochemical Sciences “A. Rossi Fanelli,” CNR Institute of Molecular Biology and Pathology and Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy
| | - Adriana E. Miele
- From the Department of Biochemical Sciences “A. Rossi Fanelli,” CNR Institute of Molecular Biology and Pathology and Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy
| | - Fulvio Saccoccia
- From the Department of Biochemical Sciences “A. Rossi Fanelli,” CNR Institute of Molecular Biology and Pathology and Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy
| | - Andrea Bellelli
- From the Department of Biochemical Sciences “A. Rossi Fanelli,” CNR Institute of Molecular Biology and Pathology and Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy
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8
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Berkholz DS, Faber HR, Savvides SN, Karplus PA. Catalytic cycle of human glutathione reductase near 1 A resolution. J Mol Biol 2008; 382:371-84. [PMID: 18638483 DOI: 10.1016/j.jmb.2008.06.083] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2008] [Revised: 06/08/2008] [Accepted: 06/26/2008] [Indexed: 11/17/2022]
Abstract
Efficient enzyme catalysis depends on exquisite details of structure beyond those resolvable in typical medium- and high-resolution crystallographic analyses. Here we report synchrotron-based cryocrystallographic studies of natural substrate complexes of the flavoenzyme human glutathione reductase (GR) at nominal resolutions between 1.1 and 0.95 A that reveal new aspects of its mechanism. Compression in the active site causes overlapping van der Waals radii and distortion in the nicotinamide ring of the NADPH substrate, which enhances catalysis via stereoelectronic effects. The bound NADPH and redox-active disulfide are positioned optimally on opposite sides of the flavin for a 1,2-addition across a flavin double bond. The new structures extend earlier observations to reveal that the redox-active disulfide loop in GR is an extreme case of sequential peptide bonds systematically deviating from planarity--a net deviation of 53 degrees across five residues. But this apparent strain is not a factor in catalysis, as it is present in both oxidized and reduced structures. Intriguingly, the flavin bond lengths in oxidized GR are intermediate between those expected for oxidized and reduced flavin, but we present evidence that this may not be due to the protein environment but instead due to partial synchrotron reduction of the flavin by the synchrotron beam. Finally, of more general relevance, we present evidence that the structures of synchrotron-reduced disulfide bonds cannot generally be used as reliable models for naturally reduced disulfide bonds.
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Affiliation(s)
- Donald S Berkholz
- Department of Biochemistry and Biophysics, Oregon State University, 2011 ALS, Corvallis, OR 97331-7305, USA
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9
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Opperman DJ, Van Heerden E. A membrane-associated protein with Cr(VI)-reducing activity from Thermus scotoductus SA-01. FEMS Microbiol Lett 2008; 280:210-8. [DOI: 10.1111/j.1574-6968.2007.01063.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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10
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Krebs G, Hugonet L, Sutherland JD. Substrate Ambiguity and Catalytic Promiscuity Within a Bacterial Proteome Probed by an Easy Phenotypic Screen for Aldehydes. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.200503031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Krebs G, Hugonet L, Sutherland JD. Substrate Ambiguity and Catalytic Promiscuity Within a Bacterial Proteome Probed by an Easy Phenotypic Screen for Aldehydes. Angew Chem Int Ed Engl 2006; 45:301-5. [PMID: 16315331 DOI: 10.1002/anie.200503031] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Guillaume Krebs
- School of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
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Brautigam CA, Chuang JL, Tomchick DR, Machius M, Chuang DT. Crystal structure of human dihydrolipoamide dehydrogenase: NAD+/NADH binding and the structural basis of disease-causing mutations. J Mol Biol 2005; 350:543-52. [PMID: 15946682 DOI: 10.1016/j.jmb.2005.05.014] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2005] [Revised: 05/02/2005] [Accepted: 05/06/2005] [Indexed: 01/08/2023]
Abstract
Human dihydrolipoamide dehydrogenase (hE3) is an enzymatic component common to the mitochondrial alpha-ketoacid dehydrogenase and glycine decarboxylase complexes. Mutations to this homodimeric flavoprotein cause the often-fatal human disease known as E3 deficiency. To catalyze the oxidation of dihydrolipoamide, hE3 uses two molecules: non-covalently bound FAD and a transiently bound substrate, NAD+. To address the catalytic mechanism of hE3 and the structural basis for E3 deficiency, the crystal structures of hE3 in the presence of NAD+ or NADH have been determined at resolutions of 2.5A and 2.1A, respectively. Although the overall fold of the enzyme is similar to that of yeast E3, these two structures differ at two loops that protrude from the proteins and at their FAD-binding sites. The structure of oxidized hE3 with NAD+ bound demonstrates that the nicotinamide moiety is not proximal to the FAD. When NADH is present, however, the nicotinamide base stacks directly on the isoalloxazine ring system of the FAD. This is the first time that this mechanistically requisite conformation of NAD+ or NADH has been observed in E3 from any species. Because E3 structures were previously available only from unicellular organisms, speculations regarding the molecular mechanisms of E3 deficiency were based on homology models. The current hE3 structures show directly that the disease-causing mutations occur at three locations in the human enzyme: the dimer interface, the active site, and the FAD and NAD(+)-binding sites. The mechanisms by which these mutations impede the function of hE3 are discussed.
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Affiliation(s)
- Chad A Brautigam
- Department of Biochemistry, The University of Texas, Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390-9038, USA.
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13
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Argyrou A, Vetting MW, Blanchard JS. Characterization of a new member of the flavoprotein disulfide reductase family of enzymes from Mycobacterium tuberculosis. J Biol Chem 2004; 279:52694-702. [PMID: 15456792 DOI: 10.1074/jbc.m410704200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The lpdA (Rv3303c) gene from Mycobacterium tuberculosis encoding a new member of the flavoprotein disulfide reductases was expressed in Escherichia coli, and the recombinant LpdA protein was purified to homogeneity. LpdA is a homotetramer and co-purifies with one molecule of tightly but noncovalently bound FAD and NADP+ per monomer. Although annotated as a probable lipoamide dehydrogenase in M. tuberculosis, LpdA cannot catalyze reduction of lipoyl substrates, because it lacks one of two cysteine residues involved in dithiol-disulfide interchange with lipoyl substrates and a His-Glu pair involved in general acid catalysis. The crystal structure of LpdA was solved by multiple isomorphous replacement with anomalous scattering, which confirmed the absence of these catalytic residues from the active site. Although LpdA cannot catalyze reduction of disulfide-bonded substrates, it catalyzes the NAD(P)H-dependent reduction of alternative electron acceptors such as 2,6-dimethyl-1,4-benzoquinone and 5-hydroxy-1,4-naphthaquinone. Significant primary deuterium kinetic isotope effects were observed with [4S-2H]NADH establishing that the enzyme promotes transfer of the C4-proS hydride of NADH. The absence of an isotope effect with [4S-2H]NADPH, the low Km value of 0.5 microm for NADPH, and the potent inhibition of the NADH-dependent reduction of 2,6-dimethyl-1,4-benzoquinone by NADP+ (Ki approximately 6 nm) and 2'-phospho-ADP-ribose (Ki approximately 800 nm), demonstrate the high affinity of LpdA for 2'-phosphorylated nucleotides and that the physiological substrate/product pair is NADPH/NADP+ rather than NADH/NAD+. Modeling of NADP+ in the active site revealed that LpdA achieves the high specificity for NADP+ through interactions involving the 2'-phosphate of NADP+ and amino acid residues that are different from those in glutathione reductase.
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Affiliation(s)
- Argyrides Argyrou
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
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14
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Argyrou A, Blanchard JS. Flavoprotein Disulfide Reductases: Advances in Chemistry and Function. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 2004; 78:89-142. [PMID: 15210329 DOI: 10.1016/s0079-6603(04)78003-4] [Citation(s) in RCA: 148] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The flavoprotein disulfide reductases represent a family of enzymes that show high sequence and structural homology. They catalyze the pyridine-nucleotide-dependent reduction of a variety of substrates, including disulfide-bonded substrates (lipoamide dehydrogenase, glutathione reductase and functional homologues, thioredoxin reductase, and alkylhydroperoxide reductase), mercuric ion (mercuric ion reductase), hydrogen peroxide (NADH peroxidase), molecular oxygen (NADH oxidase), and the reductive cleavage of a carbonyl-activated carbon-sulfur bond followed by carboxylation (2-ketopropyl-coenzyme-M carboxylase?oxidoreductase). They use at least one nonflavin redox center to transfer electrons from reduced pyridine nucleotide to their substrate through flavin adenine dinucleotide. The nature of the nonflavin redox center located adjacent to the flavin varies and three types have been identified: an enzymic disulfide (most commonly), an enzymic cysteine sulfenic acid (NADH peroxidase and NADH oxidase), and a mixed Cys-S-S-CoA disulfide (coenzyme A disulfide reductase). Selection of the particular nonflavin redox center and utilization of a second, or even a third, nonflavin redox center in some cases presumably represents the most efficient strategy for reduction of the individual substrate.
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Affiliation(s)
- Argyrides Argyrou
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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