1
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John J, Aurelius O, Srinivas V, Saura P, Kim IS, Bhowmick A, Simon PS, Dasgupta M, Pham C, Gul S, Sutherlin KD, Aller P, Butryn A, Orville AM, Cheah MH, Owada S, Tono K, Fuller FD, Batyuk A, Brewster AS, Sauter NK, Yachandra VK, Yano J, Kaila VRI, Kern J, Lebrette H, Högbom M. Redox-controlled reorganization and flavin strain within the ribonucleotide reductase R2b-NrdI complex monitored by serial femtosecond crystallography. eLife 2022; 11:79226. [PMID: 36083619 PMCID: PMC9462851 DOI: 10.7554/elife.79226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Accepted: 08/22/2022] [Indexed: 11/13/2022] Open
Abstract
Redox reactions are central to biochemistry and are both controlled by and induce protein structural changes. Here, we describe structural rearrangements and crosstalk within the Bacillus cereus ribonucleotide reductase R2b-NrdI complex, a di-metal carboxylate-flavoprotein system, as part of the mechanism generating the essential catalytic free radical of the enzyme. Femtosecond crystallography at an X-ray free electron laser was utilized to obtain structures at room temperature in defined redox states without suffering photoreduction. Together with density functional theory calculations, we show that the flavin is under steric strain in the R2b-NrdI protein complex, likely tuning its redox properties to promote superoxide generation. Moreover, a binding site in close vicinity to the expected flavin O2 interaction site is observed to be controlled by the redox state of the flavin and linked to the channel proposed to funnel the produced superoxide species from NrdI to the di-manganese site in protein R2b. These specific features are coupled to further structural changes around the R2b-NrdI interaction surface. The mechanistic implications for the control of reactive oxygen species and radical generation in protein R2b are discussed.
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Affiliation(s)
- Juliane John
- Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, Stockholm, Sweden
| | - Oskar Aurelius
- Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, Stockholm, Sweden.,MAX IV Laboratory, Lund University, Lund, Sweden
| | - Vivek Srinivas
- Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, Stockholm, Sweden
| | - Patricia Saura
- Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, Stockholm, Sweden
| | - In-Sik Kim
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, United States
| | - Asmit Bhowmick
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, United States
| | - Philipp S Simon
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, United States
| | - Medhanjali Dasgupta
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, United States
| | - Cindy Pham
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, United States
| | - Sheraz Gul
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, United States
| | - Kyle D Sutherlin
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, United States
| | - Pierre Aller
- Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot, United Kingdom.,Research Complex at Harwell, Harwell Science and Innovation Campus, Didcot, United Kingdom
| | - Agata Butryn
- Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot, United Kingdom.,Research Complex at Harwell, Harwell Science and Innovation Campus, Didcot, United Kingdom
| | - Allen M Orville
- Diamond Light Source Ltd, Harwell Science and Innovation Campus, Didcot, United Kingdom.,Research Complex at Harwell, Harwell Science and Innovation Campus, Didcot, United Kingdom
| | - Mun Hon Cheah
- Department of Chemistry - Ångström, Molecular Biomimetics, Uppsala University, Uppsala, Sweden
| | - Shigeki Owada
- Japan Synchrotron Radiation Research Institute, Sayo-gun, Japan.,RIKEN SPring-8 Center, Sayo-gun, Japan
| | - Kensuke Tono
- Japan Synchrotron Radiation Research Institute, Sayo-gun, Japan.,RIKEN SPring-8 Center, Sayo-gun, Japan
| | - Franklin D Fuller
- LCLS, SLAC National Accelerator Laboratory, Menlo Park, United States
| | - Alexander Batyuk
- LCLS, SLAC National Accelerator Laboratory, Menlo Park, United States
| | - Aaron S Brewster
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, United States
| | - Nicholas K Sauter
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, United States
| | - Vittal K Yachandra
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, United States
| | - Junko Yano
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, United States
| | - Ville R I Kaila
- Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, Stockholm, Sweden
| | - Jan Kern
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, United States
| | - Hugo Lebrette
- Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, Stockholm, Sweden
| | - Martin Högbom
- Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, Stockholm, Sweden
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2
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Banerjee R, Srinivas V, Lebrette H. Ferritin-Like Proteins: A Conserved Core for a Myriad of Enzyme Complexes. Subcell Biochem 2022; 99:109-153. [PMID: 36151375 DOI: 10.1007/978-3-031-00793-4_4] [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] [Indexed: 06/16/2023]
Abstract
Ferritin-like proteins share a common fold, a four α-helix bundle core, often coordinating a pair of metal ions. Although conserved, the ferritin fold permits a diverse set of reactions, and is central in a multitude of macromolecular enzyme complexes. Here, we emphasize this diversity through three members of the ferritin-like superfamily: the soluble methane monooxygenase, the class I ribonucleotide reductase and the aldehyde deformylating oxygenase. They all rely on dinuclear metal cofactors to catalyze different challenging oxygen-dependent reactions through the formation of multi-protein complexes. Recent studies using cryo-electron microscopy, serial femtosecond crystallography at an X-ray free electron laser source, or single-crystal X-ray diffraction, have reported the structures of the active protein complexes, and revealed unprecedented insights into the molecular mechanisms of these three enzymes.
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Affiliation(s)
- Rahul Banerjee
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Vivek Srinivas
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Hugo Lebrette
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden.
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), CNRS, UPS, Université de Toulouse, Toulouse, France.
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3
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Smethurst DGJ, Shcherbik N. Interchangeable utilization of metals: New perspectives on the impacts of metal ions employed in ancient and extant biomolecules. J Biol Chem 2021; 297:101374. [PMID: 34732319 PMCID: PMC8633580 DOI: 10.1016/j.jbc.2021.101374] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 10/25/2021] [Accepted: 10/28/2021] [Indexed: 02/08/2023] Open
Abstract
Metal ions provide considerable functionality across biological systems, and their utilization within biomolecules has adapted through changes in the chemical environment to maintain the activity they facilitate. While ancient earth's atmosphere was rich in iron and manganese and low in oxygen, periods of atmospheric oxygenation significantly altered the availability of certain metal ions, resulting in ion replacement within biomolecules. This adaptation mechanism has given rise to the phenomenon of metal cofactor interchangeability, whereby contemporary proteins and nucleic acids interact with multiple metal ions interchangeably, with different coordinated metals influencing biological activity, stability, and toxic potential. The ability of extant organisms to adapt to fluctuating metal availability remains relevant in a number of crucial biomolecules, including the superoxide dismutases of the antioxidant defense systems and ribonucleotide reductases. These well-studied and ancient enzymes illustrate the potential for metal interchangeability and adaptive utilization. More recently, the ribosome has also been demonstrated to exhibit interchangeable interactions with metal ions with impacts on function, stability, and stress adaptation. Using these and other examples, here we review the biological significance of interchangeable metal ions from a new angle that combines both biochemical and evolutionary viewpoints. The geochemical pressures and chemical properties that underlie biological metal utilization are discussed in the context of their impact on modern disease states and treatments.
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Affiliation(s)
- Daniel G J Smethurst
- Department for Cell Biology and Neuroscience, School of Osteopathic Medicine, Rowan University, Stratford, New Jersey, USA.
| | - Natalia Shcherbik
- Department for Cell Biology and Neuroscience, School of Osteopathic Medicine, Rowan University, Stratford, New Jersey, USA.
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4
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Ruskoski TB, Boal AK. The periodic table of ribonucleotide reductases. J Biol Chem 2021; 297:101137. [PMID: 34461093 PMCID: PMC8463856 DOI: 10.1016/j.jbc.2021.101137] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 08/20/2021] [Accepted: 08/26/2021] [Indexed: 12/30/2022] Open
Abstract
In most organisms, transition metal ions are necessary cofactors of ribonucleotide reductase (RNR), the enzyme responsible for biosynthesis of the 2'-deoxynucleotide building blocks of DNA. The metal ion generates an oxidant for an active site cysteine (Cys), yielding a thiyl radical that is necessary for initiation of catalysis in all RNRs. Class I enzymes, widespread in eukaryotes and aerobic microbes, share a common requirement for dioxygen in assembly of the active Cys oxidant and a unique quaternary structure, in which the metallo- or radical-cofactor is found in a separate subunit, β, from the catalytic α subunit. The first class I RNRs, the class Ia enzymes, discovered and characterized more than 30 years ago, were found to use a diiron(III)-tyrosyl-radical Cys oxidant. Although class Ia RNRs have historically served as the model for understanding enzyme mechanism and function, more recently, remarkably diverse bioinorganic and radical cofactors have been discovered in class I RNRs from pathogenic microbes. These enzymes use alternative transition metal ions, such as manganese, or posttranslationally installed tyrosyl radicals for initiation of ribonucleotide reduction. Here we summarize the recent progress in discovery and characterization of novel class I RNR radical-initiating cofactors, their mechanisms of assembly, and how they might function in the context of the active class I holoenzyme complex.
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Affiliation(s)
- Terry B Ruskoski
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Amie K Boal
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, USA; Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania, USA.
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5
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Alqurashi A, Alfs L, Swann J, Butt JN, Kelly DJ. The flavodoxin FldA activates the class Ia ribonucleotide reductase of Campylobacter jejuni. Mol Microbiol 2021; 116:343-358. [PMID: 33721378 DOI: 10.1111/mmi.14715] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 03/11/2021] [Indexed: 11/30/2022]
Abstract
Campylobacter jejuni is a microaerophilic zoonotic pathogen with an atypical respiratory Complex I that oxidizes a flavodoxin (FldA) instead of NADH. FldA is essential for viability and is reduced via pyruvate and 2-oxoglutarate oxidoreductases (POR/OOR). Here, we show that FldA can also be reduced by FqrB (Cj0559), an NADPH:FldA reductase. An fqrB deletion mutant was viable but displayed a significant growth defect. FqrB is related to flavoprotein reductases from Gram-positive bacteria that can reduce NrdI, a specialized flavodoxin that is needed for tyrosyl radical formation in NrdF, the beta subunit of class 1b-type (Mn) ribonucleotide reductase (RNR). However, C. jejuni possesses a single class Ia-type (Fe) RNR (NrdAB) that would be expected to be ferredoxin dependent. We show that CjFldA is an unusually high potential flavodoxin unrelated to NrdI, yet growth of the fqrB mutant, but not the wild-type or a complemented strain, was stimulated by low deoxyribonucleoside (dRNS) concentrations, suggesting FldA links FqrB and RNR activity. Using purified proteins, we confirmed the NrdB tyrosyl radical could be regenerated in an NADPH, FqrB, and FldA dependent manner, as evidenced by both optical and electron paramagnetic resonance (EPR) spectroscopy. Thus, FldA activates RNR in C. jejuni, partly explaining its essentiality.
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Affiliation(s)
- Abdulmajeed Alqurashi
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, UK
| | - Laura Alfs
- School of Chemistry, University of East Anglia, Norwich, UK
| | - Jordan Swann
- School of Chemistry, University of East Anglia, Norwich, UK
| | - Julea N Butt
- School of Chemistry, University of East Anglia, Norwich, UK
| | - David J Kelly
- Department of Molecular Biology and Biotechnology, The University of Sheffield, Sheffield, UK
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6
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Structure and function of an unusual flavodoxin from the domain Archaea. Proc Natl Acad Sci U S A 2019; 116:25917-25922. [PMID: 31801875 DOI: 10.1073/pnas.1908578116] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Flavodoxins, electron transfer proteins essential for diverse metabolisms in microbes from the domain Bacteria, are extensively characterized. Remarkably, although genomic annotations of flavodoxins are widespread in microbes from the domain Archaea, none have been isolated and characterized. Herein is described the structural, biochemical, and physiological characterization of an unusual flavodoxin (FldA) from Methanosarcina acetivorans, an acetate-utilizing methane-producing microbe of the domain Archaea In contrast to all flavodoxins, FldA is homodimeric, markedly less acidic, and stabilizes an anionic semiquinone. The crystal structure reveals an flavin mononucleotide (FMN) binding site unique from all other flavodoxins that provides a rationale for stabilization of the anionic semiquinone and a remarkably low reduction potentials for both the oxidized/semiquinone (-301 mV) and semiquinone/hydroquinone couples (-464 mV). FldA is up-regulated in acetate-grown versus methanol-grown cells and shown here to substitute for ferredoxin in mediating the transfer of low potential electrons from the carbonyl of acetate to the membrane-bound electron transport chain that generates ion gradients driving ATP synthesis. FldA offers potential advantages over ferredoxin by (i) sparing iron for abundant iron-sulfur proteins essential for acetotrophic growth and (ii) resilience to oxidative damage.
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7
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Aleksandrov A. A Molecular Mechanics Model for Flavins. J Comput Chem 2019; 40:2834-2842. [DOI: 10.1002/jcc.26061] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 07/03/2019] [Accepted: 08/04/2019] [Indexed: 11/06/2022]
Affiliation(s)
- Alexey Aleksandrov
- Laboratoire d'Optique et Biosciences (CNRS UMR7645, INSERM U1182), Ecole Polytechnique IP Paris, 91128 Palaiseau France
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8
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Metal-free class Ie ribonucleotide reductase from pathogens initiates catalysis with a tyrosine-derived dihydroxyphenylalanine radical. Proc Natl Acad Sci U S A 2018; 115:10022-10027. [PMID: 30224458 PMCID: PMC6176560 DOI: 10.1073/pnas.1811993115] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Conversion of ribonucleotides to the 2′-deoxyribonucleotides required for DNA biosynthesis is catalyzed by ribonucleotide reductases (RNRs) via a free-radical mechanism. Known types of RNRs all depend on redox-active transition metals—manganese, iron, or cobalt—for radical initiation. Pathogenic bacteria are challenged by transition metal sequestration and infliction of oxidative stress by their hosts, and the deployment of multiple RNRs with different metal requirements and radical-initiating oxidants is a known bacterial countermeasure. A class I RNR from two bacterial pathogens completely lacks transition metals in its active state and uses a tyrosine-derived dihydroxyphenylalanine radical as its initiator, embodying a novel tactic to combat transition metal- and oxidant-mediated innate immunity and reinforcing bacterial RNRs as potential antibiotic targets. All cells obtain 2′-deoxyribonucleotides for DNA synthesis through the activity of a ribonucleotide reductase (RNR). The class I RNRs found in humans and pathogenic bacteria differ in (i) use of Fe(II), Mn(II), or both for activation of the dinuclear-metallocofactor subunit, β; (ii) reaction of the reduced dimetal center with dioxygen or superoxide for this activation; (iii) requirement (or lack thereof) for a flavoprotein activase, NrdI, to provide the superoxide from O2; and (iv) use of either a stable tyrosyl radical or a high-valent dimetal cluster to initiate each turnover by oxidizing a cysteine residue in the α subunit to a radical (Cys•). The use of manganese by bacterial class I, subclass b-d RNRs, which contrasts with the exclusive use of iron by the eukaryotic Ia enzymes, appears to be a countermeasure of certain pathogens against iron deprivation imposed by their hosts. Here, we report a metal-free type of class I RNR (subclass e) from two human pathogens. The Cys• in its α subunit is generated by a stable, tyrosine-derived dihydroxyphenylalanine radical (DOPA•) in β. The three-electron oxidation producing DOPA• occurs in Escherichia coli only if the β is coexpressed with the NrdI activase encoded adjacently in the pathogen genome. The independence of this new RNR from transition metals, or the requirement for a single metal ion only transiently for activation, may afford the pathogens an even more potent countermeasure against transition metal-directed innate immunity.
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9
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Keirsse-Haquin J, Picaud T, Bordes L, de Gracia AG, Desbois A. Modulation of the flavin-protein interactions in NADH peroxidase and mercuric ion reductase: a resonance Raman study. EUROPEAN BIOPHYSICS JOURNAL : EBJ 2017; 47:205-223. [PMID: 28889232 DOI: 10.1007/s00249-017-1245-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 07/12/2017] [Accepted: 07/26/2017] [Indexed: 10/18/2022]
Abstract
NADH peroxidase (Npx) and mercuric ion reductase (MerA) are flavoproteins belonging to the pyridine nucleotide:disulfide oxidoreductases (PNDO) and catalyzing the reduction of toxic substrates, i.e., hydrogen peroxide and mercuric ion, respectively. To determine the role of the flavin adenine dinucleotide (FAD) in the detoxification mechanism, the resonance Raman (RR) spectra of these enzymes under various redox and ligation states have been investigated using blue and/or near-UV excitation(s). These data were compared to those previously obtained for glutathione reductase (GR), another enzyme of the PNDO family, but catalyzing the reduction of oxidized glutathione. Spectral differences have been detected for the marker bands of the isoalloxazine ring of Npx, MerA, and GR. They provide evidence for different catalytic mechanisms in these flavoproteins. The RR modes of the oxidized and two-electron reduced (EH2) forms of Npx are related to very tight flavin-protein interactions maintaining a nearly planar conformation of the isoalloxazine tricycle, a low level of H-bonding at the N1/N5 and O2/O4 sites, and a strong H-bond at N3H. They also indicate minimal changes in FAD structure and environment upon either NAD(H) binding or reduction of the sulfinic redox center. All these spectroscopic data support an enzyme functioning centered on the Cys-SO-/Cys-S- redox moiety and a neighbouring His residue. On the contrary, the RR data on various functional forms of MerA are indicative of a modulation of both ring II distortion and H-bonding states of the N5 site and ring III. The Cd(II) binding to the EH2-NADP(H) complexes, biomimetic intermediates in the reaction of Hg(II) reduction, provokes important spectral changes. They are interpreted in terms of flattening of the isoalloxazine ring and large decreases in H-bonding at the N5 site and ring III. The large flexibility of the FAD structure and environment in MerA is in agreement with proposed mechanisms involving C4a(flavin) adducts.
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Affiliation(s)
- Julie Keirsse-Haquin
- Institut de Biologie Intégrative de la Cellule, UMR 9198 CNRS-CEA-Université Paris Sud, CEA Saclay, 91191, Gif-sur-Yvette Cedex, France.,Ecole Nationale Supérieure des Mines, 44300, Nantes, France
| | - Thierry Picaud
- Institut de Biologie Intégrative de la Cellule, UMR 9198 CNRS-CEA-Université Paris Sud, CEA Saclay, 91191, Gif-sur-Yvette Cedex, France.,Institut Supérieur des Biotechnologies de Paris (Sup'Biotech Paris), 94800, Villejuif, France
| | - Luc Bordes
- Institut de Biologie Intégrative de la Cellule, UMR 9198 CNRS-CEA-Université Paris Sud, CEA Saclay, 91191, Gif-sur-Yvette Cedex, France.,School of Earth and Environmental Sciences, University of Wollongong, Wollongong, NSW, 2522, Australia
| | - Adrienne Gomez de Gracia
- Institut de Biologie Intégrative de la Cellule, UMR 9198 CNRS-CEA-Université Paris Sud, CEA Saclay, 91191, Gif-sur-Yvette Cedex, France
| | - Alain Desbois
- Institut de Biologie Intégrative de la Cellule, UMR 9198 CNRS-CEA-Université Paris Sud, CEA Saclay, 91191, Gif-sur-Yvette Cedex, France.
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10
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Lofstad M, Gudim I, Hammerstad M, Røhr ÅK, Hersleth HP. Activation of the Class Ib Ribonucleotide Reductase by a Flavodoxin Reductase in Bacillus cereus. Biochemistry 2016; 55:4998-5001. [DOI: 10.1021/acs.biochem.6b00699] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Marie Lofstad
- Section
for Biochemistry and Molecular Biology, Department of Biosciences, University of Oslo, P.O.
Box 1066, Blindern, NO-0316 Oslo, Norway
| | - Ingvild Gudim
- Section
for Biochemistry and Molecular Biology, Department of Biosciences, University of Oslo, P.O.
Box 1066, Blindern, NO-0316 Oslo, Norway
| | - Marta Hammerstad
- Section
for Biochemistry and Molecular Biology, Department of Biosciences, University of Oslo, P.O.
Box 1066, Blindern, NO-0316 Oslo, Norway
| | - Åsmund Kjendseth Røhr
- Department
of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, P.O. Box 5003, NO-1432 Ås, Norway
| | - Hans-Petter Hersleth
- Section
for Biochemistry and Molecular Biology, Department of Biosciences, University of Oslo, P.O.
Box 1066, Blindern, NO-0316 Oslo, Norway
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11
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Abstract
The development and application of a highly versatile suite of tools for mycobacterial genetics, coupled with widespread use of "omics" approaches to elucidate the structure, function, and regulation of mycobacterial proteins, has led to spectacular advances in our understanding of the metabolism and physiology of mycobacteria. In this article, we provide an update on nucleotide metabolism and DNA replication in mycobacteria, highlighting key findings from the past 10 to 15 years. In the first section, we focus on nucleotide metabolism, ranging from the biosynthesis, salvage, and interconversion of purine and pyrimidine ribonucleotides to the formation of deoxyribonucleotides. The second part of the article is devoted to DNA replication, with a focus on replication initiation and elongation, as well as DNA unwinding. We provide an overview of replication fidelity and mutation rates in mycobacteria and summarize evidence suggesting that DNA replication occurs during states of low metabolic activity, and conclude by suggesting directions for future research to address key outstanding questions. Although this article focuses primarily on observations from Mycobacterium tuberculosis, it is interspersed, where appropriate, with insights from, and comparisons with, other mycobacterial species as well as better characterized bacterial models such as Escherichia coli. Finally, a common theme underlying almost all studies of mycobacterial metabolism is the potential to identify and validate functions or pathways that can be exploited for tuberculosis drug discovery. In this context, we have specifically highlighted those processes in mycobacterial DNA replication that might satisfy this critical requirement.
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12
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Dutta SK, Serrano P, Geralt M, Axelrod HL, Xu Q, Lesley SA, Godzik A, Deacon AM, Elsliger MA, Wilson IA, Wüthrich K. Cofactor-induced reversible folding of Flavodoxin-4 from Lactobacillus acidophilus. Protein Sci 2015; 24:1600-8. [PMID: 26177955 DOI: 10.1002/pro.2743] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 06/25/2015] [Accepted: 06/26/2015] [Indexed: 11/06/2022]
Abstract
Flavodoxins in combination with the flavin mononucleotide (FMN) cofactor play important roles for electron transport in prokaryotes. Here, novel insights into the FMN-binding mechanism to flavodoxins-4 were obtained from the NMR structures of the apo-protein from Lactobacillus acidophilus (YP_193882.1) and comparison of its complex with FMN. Extensive reversible conformational changes were observed upon FMN binding and release. The NMR structure of the FMN complex is in agreement with the crystal structure (PDB ID: 3EDO) and exhibits the characteristic flavodoxin fold, with a central five-stranded parallel β-sheet and five α-helices forming an α/β-sandwich architecture. The structure differs from other flavoproteins in that helix α2 is oriented perpendicular to the β-sheet and covers the FMN-binding site. This helix reversibly unfolds upon removal of the FMN ligand, which represents a unique structural rearrangement among flavodoxins.
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Affiliation(s)
- Samit Kumar Dutta
- Joint Center for Structural Genomics, La Jolla, California, 92037.,Department of Integrative Structural and Computational Biology, the Scripps Research Institute, La Jolla, California, 92037
| | - Pedro Serrano
- Joint Center for Structural Genomics, La Jolla, California, 92037.,Department of Integrative Structural and Computational Biology, the Scripps Research Institute, La Jolla, California, 92037
| | - Michael Geralt
- Joint Center for Structural Genomics, La Jolla, California, 92037.,Department of Integrative Structural and Computational Biology, the Scripps Research Institute, La Jolla, California, 92037
| | - Herbert L Axelrod
- Joint Center for Structural Genomics, La Jolla, California, 92037.,SLAC National Accelerator Laboratory, Stanford Synchrotron Radiation Lightsource, California, 94025
| | - Qingping Xu
- Joint Center for Structural Genomics, La Jolla, California, 92037.,SLAC National Accelerator Laboratory, Stanford Synchrotron Radiation Lightsource, California, 94025
| | - Scott A Lesley
- Joint Center for Structural Genomics, La Jolla, California, 92037.,Department of Integrative Structural and Computational Biology, the Scripps Research Institute, La Jolla, California, 92037.,Protein Sciences Department, Genomics Institute of the Novartis Research Foundation, San Diego, California, 92121
| | - Adam Godzik
- Joint Center for Structural Genomics, La Jolla, California, 92037.,Program on Bioinformatics and Systems Biology, Sanford-Burnham Medical Research Institute, La Jolla, California, 92037.,Center for Research in Biological Systems, University of California, San Diego, La Jolla, California, 92093
| | - Ashley M Deacon
- Joint Center for Structural Genomics, La Jolla, California, 92037.,SLAC National Accelerator Laboratory, Stanford Synchrotron Radiation Lightsource, California, 94025
| | - Marc-André Elsliger
- Joint Center for Structural Genomics, La Jolla, California, 92037.,Department of Integrative Structural and Computational Biology, the Scripps Research Institute, La Jolla, California, 92037
| | - Ian A Wilson
- Joint Center for Structural Genomics, La Jolla, California, 92037.,Department of Integrative Structural and Computational Biology, the Scripps Research Institute, La Jolla, California, 92037.,Skaggs Institute for Chemical Biology, the Scripps Research Institute, La Jolla, California, 92037
| | - Kurt Wüthrich
- Joint Center for Structural Genomics, La Jolla, California, 92037.,Department of Integrative Structural and Computational Biology, the Scripps Research Institute, La Jolla, California, 92037.,Skaggs Institute for Chemical Biology, the Scripps Research Institute, La Jolla, California, 92037
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13
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Aurelius O, Johansson R, Bågenholm V, Lundin D, Tholander F, Balhuizen A, Beck T, Sahlin M, Sjöberg BM, Mulliez E, Logan DT. The Crystal Structure of Thermotoga maritima Class III Ribonucleotide Reductase Lacks a Radical Cysteine Pre-Positioned in the Active Site. PLoS One 2015; 10:e0128199. [PMID: 26147435 PMCID: PMC4493059 DOI: 10.1371/journal.pone.0128199] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 04/24/2015] [Indexed: 12/05/2022] Open
Abstract
Ribonucleotide reductases (RNRs) catalyze the reduction of ribonucleotides to deoxyribonucleotides, the building blocks for DNA synthesis, and are found in all but a few organisms. RNRs use radical chemistry to catalyze the reduction reaction. Despite RNR having evolved several mechanisms for generation of different kinds of essential radicals across a large evolutionary time frame, this initial radical is normally always channelled to a strictly conserved cysteine residue directly adjacent to the substrate for initiation of substrate reduction, and this cysteine has been found in the structures of all RNRs solved to date. We present the crystal structure of an anaerobic RNR from the extreme thermophile Thermotoga maritima (tmNrdD), alone and in several complexes, including with the allosteric effector dATP and its cognate substrate CTP. In the crystal structure of the enzyme as purified, tmNrdD lacks a cysteine for radical transfer to the substrate pre-positioned in the active site. Nevertheless activity assays using anaerobic cell extracts from T. maritima demonstrate that the class III RNR is enzymatically active. Other genetic and microbiological evidence is summarized indicating that the enzyme is important for T. maritima. Mutation of either of two cysteine residues in a disordered loop far from the active site results in inactive enzyme. We discuss the possible mechanisms for radical initiation of substrate reduction given the collected evidence from the crystal structure, our activity assays and other published work. Taken together, the results suggest either that initiation of substrate reduction may involve unprecedented conformational changes in the enzyme to bring one of these cysteine residues to the expected position, or that alternative routes for initiation of the RNR reduction reaction may exist. Finally, we present a phylogenetic analysis showing that the structure of tmNrdD is representative of a new RNR subclass IIIh, present in all Thermotoga species plus a wider group of bacteria from the distantly related phyla Firmicutes, Bacteroidetes and Proteobacteria.
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Affiliation(s)
- Oskar Aurelius
- Dept. of Biochemistry & Structural Biology, Lund University, Box 124, S-221 00 Lund, Sweden
| | - Renzo Johansson
- Dept. of Biochemistry & Structural Biology, Lund University, Box 124, S-221 00 Lund, Sweden
| | - Viktoria Bågenholm
- Dept. of Biochemistry & Structural Biology, Lund University, Box 124, S-221 00 Lund, Sweden
| | - Daniel Lundin
- Dept. of Biochemistry & Biophysics, Stockholm University, S-106 91 Stockholm, Sweden
| | - Fredrik Tholander
- Dept. of Medical Biochemistry and Biophysics, Karolinska Institute, Solna, Sweden
| | - Alexander Balhuizen
- Dept. of Biochemistry & Structural Biology, Lund University, Box 124, S-221 00 Lund, Sweden
| | - Tobias Beck
- Dept. of Inorganic Chemistry, Georg-August Universität Göttingen, Göttingen, Germany
| | - Margareta Sahlin
- Dept. of Biochemistry & Biophysics, Stockholm University, S-106 91 Stockholm, Sweden
| | - Britt-Marie Sjöberg
- Dept. of Biochemistry & Biophysics, Stockholm University, S-106 91 Stockholm, Sweden
| | - Etienne Mulliez
- LCBM, Groupe de Biocatalyse, CEA-Grenoble, Institut de Recherches en Technologies et Sciences pour le Vivant (iRTSV), 38054 Grenoble Cedex 09, France
| | - Derek T. Logan
- Dept. of Biochemistry & Structural Biology, Lund University, Box 124, S-221 00 Lund, Sweden
- * E-mail:
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14
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Golden E, Karton A, Vrielink A. High-resolution structures of cholesterol oxidase in the reduced state provide insights into redox stabilization. ACTA ACUST UNITED AC 2014; 70:3155-66. [PMID: 25478834 DOI: 10.1107/s139900471402286x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 10/17/2014] [Indexed: 01/09/2023]
Abstract
Cholesterol oxidase (CO) is a flavoenzyme that catalyzes the oxidation and isomerization of cholesterol to cholest-4-en-3-one. The reductive half reaction occurs via a hydride transfer from the substrate to the FAD cofactor. The structures of CO reduced with dithionite under aerobic conditions and in the presence of the substrate 2-propanol under both aerobic and anaerobic conditions are presented. The 1.32 Å resolution structure of the dithionite-reduced enzyme reveals a sulfite molecule covalently bound to the FAD cofactor. The isoalloxazine ring system displays a bent structure relative to that of the oxidized enzyme, and alternate conformations of a triad of aromatic residues near to the cofactor are evident. A 1.12 Å resolution anaerobically trapped reduced enzyme structure in the presence of 2-propanol does not show a similar bending of the flavin ring system, but does show alternate conformations of the aromatic triad. Additionally, a significant difference electron-density peak is observed within a covalent-bond distance of N5 of the flavin moiety, suggesting that a hydride-transfer event has occurred as a result of substrate oxidation trapping the flavin in the electron-rich reduced state. The hydride transfer generates a tetrahedral geometry about the flavin N5 atom. High-level density-functional theory calculations were performed to correlate the crystallographic findings with the energetics of this unusual arrangement of the flavin moiety. These calculations suggest that strong hydrogen-bond interactions between Gly120 and the flavin N5 centre may play an important role in these structural features.
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Affiliation(s)
- Emily Golden
- School of Chemistry and Biochemistry, University of Western Australia, Crawley, Western Australia 6009, Australia
| | - Amir Karton
- School of Chemistry and Biochemistry, University of Western Australia, Crawley, Western Australia 6009, Australia
| | - Alice Vrielink
- School of Chemistry and Biochemistry, University of Western Australia, Crawley, Western Australia 6009, Australia
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15
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Berggren G, Duraffourg N, Sahlin M, Sjöberg BM. Semiquinone-induced maturation of Bacillus anthracis ribonucleotide reductase by a superoxide intermediate. J Biol Chem 2014; 289:31940-31949. [PMID: 25262022 DOI: 10.1074/jbc.m114.592535] [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] [Indexed: 11/06/2022] Open
Abstract
Ribonucleotide reductases (RNRs) catalyze the conversion of ribonucleotides to deoxyribonucleotides, and represent the only de novo pathway to provide DNA building blocks. Three different classes of RNR are known, denoted I-III. Class I RNRs are heteromeric proteins built up by α and β subunits and are further divided into different subclasses, partly based on the metal content of the β-subunit. In subclass Ib RNR the β-subunit is denoted NrdF, and harbors a manganese-tyrosyl radical cofactor. The generation of this cofactor is dependent on a flavodoxin-like maturase denoted NrdI, responsible for the formation of an active oxygen species suggested to be either a superoxide or a hydroperoxide. Herein we report on the magnetic properties of the manganese-tyrosyl radical cofactor of Bacillus anthracis NrdF and the redox properties of B. anthracis NrdI. The tyrosyl radical in NrdF is stabilized through its interaction with a ferromagnetically coupled manganese dimer. Moreover, we show through a combination of redox titration and protein electrochemistry that in contrast to hitherto characterized NrdIs, the B. anthracis NrdI is stable in its semiquinone form (NrdIsq) with a difference in electrochemical potential of ∼110 mV between the hydroquinone and semiquinone state. The under anaerobic conditions stable NrdIsq is fully capable of generating the oxidized, tyrosyl radical-containing form of Mn-NrdF when exposed to oxygen. This latter observation strongly supports that a superoxide radical is involved in the maturation mechanism, and contradicts the participation of a peroxide species. Additionally, EPR spectra on whole cells revealed that a significant fraction of NrdI resides in its semiquinone form in vivo, underscoring that NrdIsq is catalytically relevant.
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Affiliation(s)
- Gustav Berggren
- Department of Biochemistry and Biophysics, Stockholm University SE-10691 Stockholm, Sweden and
| | - Nicolas Duraffourg
- Laboratoire de Chimie et Biologie des Métaux (UMR 5249), CEA-Grenoble, 17, rue des Martyrs, F-38057 Grenoble, France
| | - Margareta Sahlin
- Department of Biochemistry and Biophysics, Stockholm University SE-10691 Stockholm, Sweden and
| | - Britt-Marie Sjöberg
- Department of Biochemistry and Biophysics, Stockholm University SE-10691 Stockholm, Sweden and.
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16
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Hammerstad M, Hersleth HP, Tomter AB, Røhr ÅK, Andersson KK. Crystal structure of Bacillus cereus class Ib ribonucleotide reductase di-iron NrdF in complex with NrdI. ACS Chem Biol 2014; 9:526-37. [PMID: 24295378 DOI: 10.1021/cb400757h] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Class Ib ribonucleotide reductases (RNRs) use a dimetal-tyrosyl radical (Y•) cofactor in their NrdF (β2) subunit to initiate ribonucleotide reduction in the NrdE (α2) subunit. Contrary to the diferric tyrosyl radical (Fe(III)2-Y•) cofactor, which can self-assemble from Fe(II)2-NrdF and O2, generation of the Mn(III)2-Y• cofactor requires the reduced form of a flavoprotein, NrdIhq, and O2 for its assembly. Here we report the 1.8 Å resolution crystal structure of Bacillus cereus Fe2-NrdF in complex with NrdI. Compared to the previously solved Escherichia coli NrdI-Mn(II)2-NrdF structure, NrdI and NrdF binds similarly in Bacillus cereus through conserved core interactions. This protein-protein association seems to be unaffected by metal ion type bound in the NrdF subunit. The Bacillus cereus Mn(II)2-NrdF and Fe2-NrdF structures, also presented here, show conformational flexibility of residues surrounding the NrdF metal ion site. The movement of one of the metal-coordinating carboxylates is linked to the metal type present at the dimetal site and not associated with NrdI-NrdF binding. This carboxylate conformation seems to be vital for the water network connecting the NrdF dimetal site and the flavin in NrdI. From these observations, we suggest that metal-dependent variations in carboxylate coordination geometries are important for active Y• cofactor generation in class Ib RNRs. Additionally, we show that binding of NrdI to NrdF would structurally interfere with the suggested α2β2 (NrdE-NrdF) holoenzyme formation, suggesting the potential requirement for NrdI dissociation before NrdE-NrdF assembly after NrdI-activation. The mode of interactions between the proteins involved in the class Ib RNR system is, however, not fully resolved.
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Affiliation(s)
- Marta Hammerstad
- Department of Biosciences, University of Oslo, P.O.
Box 1066, Blindern, NO-0316 Oslo, Norway
| | - Hans-Petter Hersleth
- Department of Biosciences, University of Oslo, P.O.
Box 1066, Blindern, NO-0316 Oslo, Norway
| | - Ane B. Tomter
- Department of Biosciences, University of Oslo, P.O.
Box 1066, Blindern, NO-0316 Oslo, Norway
| | - Åsmund K. Røhr
- Department of Biosciences, University of Oslo, P.O.
Box 1066, Blindern, NO-0316 Oslo, Norway
| | - K. Kristoffer Andersson
- Department of Biosciences, University of Oslo, P.O.
Box 1066, Blindern, NO-0316 Oslo, Norway
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17
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Makhlynets O, Boal AK, Rhodes DV, Kitten T, Rosenzweig AC, Stubbe J. Streptococcus sanguinis class Ib ribonucleotide reductase: high activity with both iron and manganese cofactors and structural insights. J Biol Chem 2013; 289:6259-72. [PMID: 24381172 DOI: 10.1074/jbc.m113.533554] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Streptococcus sanguinis is a causative agent of infective endocarditis. Deletion of SsaB, a manganese transporter, drastically reduces S. sanguinis virulence. Many pathogenic organisms require class Ib ribonucleotide reductase (RNR) to catalyze the conversion of nucleotides to deoxynucleotides under aerobic conditions, and recent studies demonstrate that this enzyme uses a dimanganese-tyrosyl radical (Mn(III)2-Y(•)) cofactor in vivo. The proteins required for S. sanguinis ribonucleotide reduction (NrdE and NrdF, α and β subunits of RNR; NrdH and TrxR, a glutaredoxin-like thioredoxin and a thioredoxin reductase; and NrdI, a flavodoxin essential for assembly of the RNR metallo-cofactor) have been identified and characterized. Apo-NrdF with Fe(II) and O2 can self-assemble a diferric-tyrosyl radical (Fe(III)2-Y(•)) cofactor (1.2 Y(•)/β2) and with the help of NrdI can assemble a Mn(III)2-Y(•) cofactor (0.9 Y(•)/β2). The activity of RNR with its endogenous reductants, NrdH and TrxR, is 5,000 and 1,500 units/mg for the Mn- and Fe-NrdFs (Fe-loaded NrdF), respectively. X-ray structures of S. sanguinis NrdIox and Mn(II)2-NrdF are reported and provide a possible rationale for the weak affinity (2.9 μM) between them. These streptococcal proteins form a structurally distinct subclass relative to other Ib proteins with unique features likely important in cluster assembly, including a long and negatively charged loop near the NrdI flavin and a bulky residue (Thr) at a constriction in the oxidant channel to the NrdI interface. These studies set the stage for identifying the active form of S. sanguinis class Ib RNR in an animal model for infective endocarditis and establishing whether the manganese requirement for pathogenesis is associated with RNR.
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18
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Huang WC, Ellis J, Moody P, Raven E, Roberts G. Redox-linked domain movements in the catalytic cycle of cytochrome p450 reductase. Structure 2013; 21:1581-9. [PMID: 23911089 PMCID: PMC3763376 DOI: 10.1016/j.str.2013.06.022] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Revised: 06/24/2013] [Accepted: 06/26/2013] [Indexed: 11/17/2022]
Abstract
NADPH-cytochrome P450 reductase is a key component of the P450 mono-oxygenase drug-metabolizing system. There is evidence for a conformational equilibrium involving large-scale domain motions in this enzyme. We now show, using small-angle X-ray scattering (SAXS) and small-angle neutron scattering, that delivery of two electrons to cytochrome P450 reductase leads to a shift in this equilibrium from a compact form, similar to the crystal structure, toward an extended form, while coenzyme binding favors the compact form. We present a model for the extended form of the enzyme based on nuclear magnetic resonance and SAXS data. Using the effects of changes in solution conditions and of site-directed mutagenesis, we demonstrate that the conversion to the extended form leads to an enhanced ability to transfer electrons to cytochrome c. This structural evidence shows that domain motion is linked closely to the individual steps of the catalytic cycle of cytochrome P450 reductase, and we propose a mechanism for this.
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Affiliation(s)
- Wei-Cheng Huang
- Henry Wellcome Laboratories for Structural Biology, Department of Biochemistry, University of Leicester, Henry Wellcome Building, Leicester LE1 9HN, UK
| | - Jacqueline Ellis
- Henry Wellcome Laboratories for Structural Biology, Department of Biochemistry, University of Leicester, Henry Wellcome Building, Leicester LE1 9HN, UK
| | - Peter C.E. Moody
- Henry Wellcome Laboratories for Structural Biology, Department of Biochemistry, University of Leicester, Henry Wellcome Building, Leicester LE1 9HN, UK
| | - Emma L. Raven
- Department of Chemistry, University of Leicester, Leicester LE1 7RH, UK
| | - Gordon C.K. Roberts
- Henry Wellcome Laboratories for Structural Biology, Department of Biochemistry, University of Leicester, Henry Wellcome Building, Leicester LE1 9HN, UK
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19
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Roos K, Siegbahn PEM. Activation of Dimanganese Class Ib Ribonucleotide Reductase by Hydrogen Peroxide: Mechanistic Insights from Density Functional Theory. Inorg Chem 2013; 52:4173-84. [DOI: 10.1021/ic3008427] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Katarina Roos
- Department of Physics, Stockholm University, SE-106 91 Stockholm,
Sweden
| | - Per E. M. Siegbahn
- Department of Physics, Stockholm University, SE-106 91 Stockholm,
Sweden
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20
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Cotruvo JA, Stich TA, Britt RD, Stubbe J. Mechanism of assembly of the dimanganese-tyrosyl radical cofactor of class Ib ribonucleotide reductase: enzymatic generation of superoxide is required for tyrosine oxidation via a Mn(III)Mn(IV) intermediate. J Am Chem Soc 2013; 135:4027-39. [PMID: 23402532 DOI: 10.1021/ja312457t] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ribonucleotide reductases (RNRs) utilize radical chemistry to reduce nucleotides to deoxynucleotides in all organisms. In the class Ia and Ib RNRs, this reaction requires a stable tyrosyl radical (Y(•)) generated by oxidation of a reduced dinuclear metal cluster. The Fe(III)2-Y(•) cofactor in the NrdB subunit of the class Ia RNRs can be generated by self-assembly from Fe(II)2-NrdB, O2, and a reducing equivalent. By contrast, the structurally homologous class Ib enzymes require a Mn(III)2-Y(•) cofactor in their NrdF subunit. Mn(II)2-NrdF does not react with O2, but it binds the reduced form of a conserved flavodoxin-like protein, NrdIhq, which, in the presence of O2, reacts to form the Mn(III)2-Y(•) cofactor. Here we investigate the mechanism of assembly of the Mn(III)2-Y(•) cofactor in Bacillus subtilis NrdF. Cluster assembly from Mn(II)2-NrdF, NrdI(hq), and O2 has been studied by stopped flow absorption and rapid freeze quench EPR spectroscopies. The results support a mechanism in which NrdI(hq) reduces O2 to O2(•-) (40-48 s(-1), 0.6 mM O2), the O2(•-) channels to and reacts with Mn(II)2-NrdF to form a Mn(III)Mn(IV) intermediate (2.2 ± 0.4 s(-1)), and the Mn(III)Mn(IV) species oxidizes tyrosine to Y(•) (0.08-0.15 s(-1)). Controlled production of O2(•-) by NrdIhq during class Ib RNR cofactor assembly both circumvents the unreactivity of the Mn(II)2 cluster with O2 and satisfies the requirement for an "extra" reducing equivalent in Y(•) generation.
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Affiliation(s)
- Joseph A Cotruvo
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
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21
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Gustafsson TN, Sahlin M, Lu J, Sjöberg BM, Holmgren A. Bacillus anthracis thioredoxin systems, characterization and role as electron donors for ribonucleotide reductase. J Biol Chem 2012; 287:39686-97. [PMID: 23012357 DOI: 10.1074/jbc.m112.413427] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Bacillus anthracis is the causative agent of anthrax, which is associated with a high mortality rate. Like several medically important bacteria, B. anthracis lacks glutathione but encodes many genes annotated as thioredoxins, thioredoxin reductases, and glutaredoxin-like proteins. We have cloned, expressed, and characterized three potential thioredoxins, two potential thioredoxin reductases, and three glutaredoxin-like proteins. Of these, thioredoxin 1 (Trx1) and NrdH reduced insulin, 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), and the manganese-containing type Ib ribonucleotide reductase (RNR) from B. anthracis in the presence of NADPH and thioredoxin reductase 1 (TR1), whereas thioredoxin 2 (Trx2) could only reduce DTNB. Potential TR2 was verified as an FAD-containing protein reducible by dithiothreitol but not by NAD(P)H. The recently discovered monothiol bacillithiol did not work as a reductant for RNR, either directly or via any of the redoxins. The catalytic efficiency of Trx1 was 3 and 20 times higher than that of Trx2 and NrdH, respectively, as substrates for TR1. Additionally, the catalytic efficiency of Trx1 as an electron donor for RNR was 7-fold higher than that of NrdH. In extracts of B. anthracis, Trx1 was responsible for almost all of the disulfide reductase activity, whereas Western blots showed that the level of Trx1 was 15 and 60 times higher than that of Trx2 and NrdH, respectively. Our findings demonstrate that the most important general disulfide reductase system in B. anthracis is TR1/Trx1 and that Trx1 is the physiologically relevant electron donor for RNR. This information may provide a basis for the development of novel antimicrobial therapies targeting this severe pathogen.
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Affiliation(s)
- Tomas N Gustafsson
- Division of Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institutet SE-17177 Stockholm, Sweden
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22
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Boal AK, Cotruvo JA, Stubbe J, Rosenzweig AC. The dimanganese(II) site of Bacillus subtilis class Ib ribonucleotide reductase. Biochemistry 2012; 51:3861-71. [PMID: 22443445 DOI: 10.1021/bi201925t] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Class Ib ribonucleotide reductases (RNRs) use a dimanganese-tyrosyl radical cofactor, Mn(III)(2)-Y(•), in their homodimeric NrdF (β2) subunit to initiate reduction of ribonucleotides to deoxyribonucleotides. The structure of the Mn(II)(2) form of NrdF is an important component in understanding O(2)-mediated formation of the active metallocofactor, a subject of much interest because a unique flavodoxin, NrdI, is required for cofactor assembly. Biochemical studies and sequence alignments suggest that NrdF and NrdI proteins diverge into three phylogenetically distinct groups. The only crystal structure to date of a NrdF with a fully ordered and occupied dimanganese site is that of Escherichia coli Mn(II)(2)-NrdF, prototypical of the enzymes from actinobacteria and proteobacteria. Here we report the 1.9 Å resolution crystal structure of Bacillus subtilis Mn(II)(2)-NrdF, representative of the enzymes from a second group, from Bacillus and Staphylococcus. The structures of the metal clusters in the β2 dimer are distinct from those observed in E. coli Mn(II)(2)-NrdF. These differences illustrate the key role that solvent molecules and protein residues in the second coordination sphere of the Mn(II)(2) cluster play in determining conformations of carboxylate residues at the metal sites and demonstrate that diverse coordination geometries are capable of serving as starting points for Mn(III)(2)-Y(•) cofactor assembly in class Ib RNRs.
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Affiliation(s)
- Amie K Boal
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, USA
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23
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Spectroscopic studies of the iron and manganese reconstituted tyrosyl radical in Bacillus cereus ribonucleotide reductase R2 protein. PLoS One 2012; 7:e33436. [PMID: 22432022 PMCID: PMC3303829 DOI: 10.1371/journal.pone.0033436] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Accepted: 02/08/2012] [Indexed: 11/24/2022] Open
Abstract
Ribonucleotide reductase (RNR) catalyzes the rate limiting step in DNA synthesis where ribonucleotides are reduced to the corresponding deoxyribonucleotides. Class Ib RNRs consist of two homodimeric subunits: R1E, which houses the active site; and R2F, which contains a metallo cofactor and a tyrosyl radical that initiates the ribonucleotide reduction reaction. We studied the R2F subunit of B. cereus reconstituted with iron or alternatively with manganese ions, then subsequently reacted with molecular oxygen to generate two tyrosyl-radicals. The two similar X-band EPR spectra did not change significantly over 4 to 50 K. From the 285 GHz EPR spectrum of the iron form, a g1-value of 2.0090 for the tyrosyl radical was extracted. This g1-value is similar to that observed in class Ia E. coli R2 and class Ib R2Fs with iron-oxygen cluster, suggesting the absence of hydrogen bond to the phenoxyl group. This was confirmed by resonance Raman spectroscopy, where the stretching vibration associated to the radical (C-O, ν7a = 1500 cm−1) was found to be insensitive to deuterium-oxide exchange. Additionally, the 18O-sensitive Fe-O-Fe symmetric stretching (483 cm−1) of the metallo-cofactor was also insensitive to deuterium-oxide exchange indicating no hydrogen bonding to the di-iron-oxygen cluster, and thus, different from mouse R2 with a hydrogen bonded cluster. The HF-EPR spectrum of the manganese reconstituted RNR R2F gave a g1-value of ∼2.0094. The tyrosyl radical microwave power saturation behavior of the iron-oxygen cluster form was as observed in class Ia R2, with diamagnetic di-ferric cluster ground state, while the properties of the manganese reconstituted form indicated a magnetic ground state of the manganese-cluster. The recent activity measurements (Crona et al., (2011) J Biol Chem 286: 33053–33060) indicates that both the manganese and iron reconstituted RNR R2F could be functional. The manganese form might be very important, as it has 8 times higher activity.
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24
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Cotruvo JA, Stubbe J. Class I ribonucleotide reductases: metallocofactor assembly and repair in vitro and in vivo. Annu Rev Biochem 2011; 80:733-67. [PMID: 21456967 DOI: 10.1146/annurev-biochem-061408-095817] [Citation(s) in RCA: 159] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Incorporation of metallocofactors essential for the activity of many enyzmes is a major mechanism of posttranslational modification. The cellular machinery required for these processes in the case of mono- and dinuclear nonheme iron and manganese cofactors has remained largely elusive. In addition, many metallocofactors can be converted to inactive forms, and pathways for their repair have recently come to light. The class I ribonucleotide reductases (RNRs) catalyze the conversion of nucleotides to deoxynucleotides and require dinuclear metal clusters for activity: an Fe(III)Fe(III)-tyrosyl radical (Y•) cofactor (class Ia), a Mn(III)Mn(III)-Y• cofactor (class Ib), and a Mn(IV)Fe(III) cofactor (class Ic). The class Ia, Ib, and Ic RNRs are structurally homologous and contain almost identical metal coordination sites. Recent progress in our understanding of the mechanisms by which the cofactor of each of these RNRs is generated in vitro and in vivo and by which the damaged cofactors are repaired is providing insight into how nature prevents mismetallation and orchestrates active cluster formation in high yields.
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Affiliation(s)
- Joseph A Cotruvo
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
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25
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Crona M, Torrents E, Røhr AK, Hofer A, Furrer E, Tomter AB, Andersson KK, Sahlin M, Sjöberg BM. NrdH-redoxin protein mediates high enzyme activity in manganese-reconstituted ribonucleotide reductase from Bacillus anthracis. J Biol Chem 2011; 286:33053-60. [PMID: 21832039 PMCID: PMC3190916 DOI: 10.1074/jbc.m111.278119] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bacillus anthracis is a severe mammalian pathogen encoding a class Ib ribonucleotide reductase (RNR). RNR is a universal enzyme that provides the four essential deoxyribonucleotides needed for DNA replication and repair. Almost all Bacillus spp. encode both class Ib and class III RNR operons, but the B. anthracis class III operon was reported to encode a pseudogene, and conceivably class Ib RNR is necessary for spore germination and proliferation of B. anthracis upon infection. The class Ib RNR operon in B. anthracis encodes genes for the catalytic NrdE protein, the tyrosyl radical metalloprotein NrdF, and the flavodoxin protein NrdI. The tyrosyl radical in NrdF is stabilized by an adjacent Mn(2)(III) site (Mn-NrdF) formed by the action of the NrdI protein or by a Fe(2)(III) site (Fe-NrdF) formed spontaneously from Fe(2+) and O(2). In this study, we show that the properties of B. anthracis Mn-NrdF and Fe-NrdF are in general similar for interaction with NrdE and NrdI. Intriguingly, the enzyme activity of Mn-NrdF was approximately an order of magnitude higher than that of Fe-NrdF in the presence of the class Ib-specific physiological reductant NrdH, strongly suggesting that the Mn-NrdF form is important in the life cycle of B. anthracis. Whether the Fe-NrdF form only exists in vitro or whether the NrdF protein in B. anthracis is a true cambialistic enzyme that can work with either manganese or iron remains to be established.
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Affiliation(s)
- Mikael Crona
- Department of Molecular Biology and Functional Genomics, Arrhenius Laboratories for Natural Sciences, Stockholm University SE-10691 Stockholm, Sweden
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Zhang Y, Stubbe J. Bacillus subtilis class Ib ribonucleotide reductase is a dimanganese(III)-tyrosyl radical enzyme. Biochemistry 2011; 50:5615-23. [PMID: 21561096 DOI: 10.1021/bi200348q] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Bacillus subtilis class Ib ribonucleotide reductase (RNR) catalyzes the conversion of nucleotides to deoxynucleotides, providing the building blocks for DNA replication and repair. It is composed of two proteins: α (NrdE) and β (NrdF). β contains the metallo-cofactor, essential for the initiation of the reduction process. The RNR genes are organized within the nrdI-nrdE-nrdF-ymaB operon. Each protein has been cloned, expressed, and purified from Escherichia coli. As isolated, recombinant NrdF (rNrdF) contained a diferric-tyrosyl radical [Fe(III)(2)-Y(•)] cofactor. Alternatively, this cluster could be self-assembled from apo-rNrdF, Fe(II), and O(2). Apo-rNrdF loaded using 4 Mn(II)/β(2), O(2), and reduced NrdI (a flavodoxin) can form a dimanganese(III)-Y(•) [Mn(III)(2)-Y(•)] cofactor. In the presence of rNrdE, ATP, and CDP, Mn(III)(2)-Y(•) and Fe(III)(2)-Y(•) rNrdF generate dCDP at rates of 132 and 10 nmol min(-1) mg(-1), respectively (both normalized for 1 Y(•)/β(2)). To determine the endogenous cofactor of NrdF in B. subtilis, the entire operon was placed behind a Pspank(hy) promoter and integrated into the B. subtilis genome at the amyE site. All four genes were induced in cells grown in Luria-Bertani medium, with levels of NrdE and NrdF elevated 35-fold relative to that of the wild-type strain. NrdE and NrdF were copurified in a 1:1 ratio from this engineered B. subtilis. The visible, EPR, and atomic absorption spectra of the purified NrdENrdF complex (eNrdF) exhibited characteristics of a Mn(III)(2)-Y(•) center with 2 Mn/β(2) and 0.5 Y(•)/β(2) and an activity of 318-363 nmol min(-1) mg(-1) (normalized for 1 Y(•)/β(2)). These data strongly suggest that the B. subtilis class Ib RNR is a Mn(III)(2)-Y(•) enzyme.
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Affiliation(s)
- Yan Zhang
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Cotruvo JA, Stubbe J. Escherichia coli class Ib ribonucleotide reductase contains a dimanganese(III)-tyrosyl radical cofactor in vivo. Biochemistry 2011; 50:1672-81. [PMID: 21250660 DOI: 10.1021/bi101881d] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Escherichia coli class Ib ribonucleotide reductase (RNR) converts nucleoside 5'-diphosphates to deoxynucleoside 5'-diphosphates in iron-limited and oxidative stress conditions. We have recently demonstrated in vitro that this RNR is active with both diferric-tyrosyl radical (Fe(III)(2)-Y(•)) and dimanganese(III)-Y(•) (Mn(III)(2)-Y(•)) cofactors in the β2 subunit, NrdF [Cotruvo, J. A., Jr., and Stubbe, J. (2010) Biochemistry 49, 1297-1309]. Here we demonstrate, by purification of this protein from its endogenous levels in an E. coli strain deficient in its five known iron uptake pathways and grown under iron-limited conditions, that the Mn(III)(2)-Y(•) cofactor is assembled in vivo. This is the first definitive determination of the active cofactor of a class Ib RNR purified from its native organism without overexpression. From 88 g of cell paste, 150 μg of NrdF was isolated with ∼95% purity, with 0.2 Y(•)/β2, 0.9 Mn/β2, and a specific activity of 720 nmol min(-1) mg(-1). Under these conditions, the class Ib RNR is the primary active RNR in the cell. Our results strongly suggest that E. coli NrdF is an obligate manganese protein in vivo and that the Mn(III)(2)-Y(•) cofactor assembly pathway we have identified in vitro involving the flavodoxin-like protein NrdI, present inside the cell at catalytic levels, is operative in vivo.
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Affiliation(s)
- Joseph A Cotruvo
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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Affiliation(s)
- Britt-Marie Sjöberg
- Department of Molecular Biology and Functional Genomics, Stockholm University, SE-10691 Stockholm, Sweden.
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