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Krause T, Keshavarzi B, Heitkam S, Ansorge-Schumacher MB. Foam fractionation Tags (F-Tags) enabling surfactant-free, activity-preserving recovery of enzymes. Appl Microbiol Biotechnol 2024; 108:140. [PMID: 38231394 PMCID: PMC10794386 DOI: 10.1007/s00253-023-12837-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 10/05/2023] [Accepted: 10/20/2023] [Indexed: 01/18/2024]
Abstract
Enzymes have become important tools in many industries. However, the full exploitation of their potential is currently limited by a lack of efficient and cost-effective methods for enzyme purification from microbial production. One technology that could solve this problem is foam fractionation. In this study, we show that diverse natural foam-stabilizing proteins fused as F-Tags to β-lactamase, penicillin G acylase, and formate dehydrogenase, respectively, are able to mediate foaming and recovery of the enzymes by foam fractionation. The catalytic activity of all three candidates is largely preserved. Under appropriate fractionation conditions, especially when a wash buffer is used, some F-Tags also allow nearly complete separation of the target enzyme from a contaminating protein. We found that a larger distance between the F-Tag and the target enzyme has a positive effect on the maintenance of catalytic activity. However, we did not identify any particular sequence motifs or physical parameters that influenced performance as an F-tag. The best results were obtained with a short helical F-Tag, which was originally intended to serve only as a linker sequence. The findings of the study suggest that the development of molecular tags that enable the establishment of surfactant-free foam fractionation for enzyme workup is a promising method. KEY POINTS: • Foam-stabilizing proteins mediate activity-preserving foam fractionation of enzymes • Performance as an F-Tag is not restricted to particular structural motifs • Separation from untagged protein benefits from low foam stability and foam washings.
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Affiliation(s)
- Thomas Krause
- Department of Molecular Biotechnology, TU Dresden, 01062, Dresden, Germany
| | - Behnam Keshavarzi
- Institute of Process Engineering and Environmental Technology, TU Dresden, 01062, Dresden, Germany
| | - Sascha Heitkam
- Institute of Process Engineering and Environmental Technology, TU Dresden, 01062, Dresden, Germany
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2
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Burnim AA, Xu D, Spence MA, Jackson CJ, Ando N. Analysis of insertions and extensions in the functional evolution of the ribonucleotide reductase family. Protein Sci 2022; 31:e4483. [PMID: 36307939 PMCID: PMC9669993 DOI: 10.1002/pro.4483] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 10/22/2022] [Indexed: 12/14/2022]
Abstract
Ribonucleotide reductases (RNRs) are used by all free-living organisms and many viruses to catalyze an essential step in the de novo biosynthesis of DNA precursors. RNRs are remarkably diverse by primary sequence and cofactor requirement, while sharing a conserved fold and radical-based mechanism for nucleotide reduction. In this work, we expand on our recent phylogenetic inference of the entire RNR family and describe the evolutionarily relatedness of insertions and extensions around the structurally homologous catalytic barrel. Using evo-velocity and sequence similarity network (SSN) analyses, we show that the N-terminal regulatory motif known as the ATP-cone domain was likely inherited from an ancestral RNR. By combining SSN analysis with AlphaFold2 predictions, we also show that the C-terminal extensions of class II RNRs can contain folded domains that share homology with an Fe-S cluster assembly protein. Finally, using sequence analysis and AlphaFold2, we show that the sequence motif of a catalytically essential insertion known as the finger loop is tightly coupled to the catalytic mechanism. Based on these results, we propose an evolutionary model for the diversification of the RNR family.
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Affiliation(s)
- Audrey A. Burnim
- Department of Chemistry and Chemical BiologyCornell UniversityIthacaNew YorkUSA
| | - Da Xu
- Department of Chemistry and Chemical BiologyCornell UniversityIthacaNew YorkUSA
| | - Matthew A. Spence
- Research School of ChemistryAustralian National UniversityCanberraAustralian Capital TerritoryAustralia
| | - Colin J. Jackson
- Research School of ChemistryAustralian National UniversityCanberraAustralian Capital TerritoryAustralia
- Australian Research Council Centre of Excellence for Innovations in Peptide and Protein ScienceAustralian National UniversityCanberraAustralian Capital TerritoryAustralia
- Australian Research Council Centre of Excellence in Synthetic BiologyAustralian National UniversityCanberraAustralian Capital TerritoryAustralia
| | - Nozomi Ando
- Department of Chemistry and Chemical BiologyCornell UniversityIthacaNew YorkUSA
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3
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Fietze T, Wilk P, Kabinger F, Anoosheh S, Hofer A, Lundin D, Feiler CG, Weiss MS, Loderer C. HUG Domain Is Responsible for Active Dimer Stabilization in an NrdJd Ribonucleotide Reductase. Biochemistry 2022; 61:1633-1641. [PMID: 35856337 DOI: 10.1021/acs.biochem.2c00173] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ribonucleotide reductases (RNRs) catalyze the reduction of ribonucleotides to the corresponding deoxyribonucleotides. The catalytic activity of most RNRs depends on the formation of a dimer of the catalytic subunits. The active site is located at the interface, and part of the substrate binding site and regulatory mechanisms work across the subunit in the dimer. In this study, we describe and characterize a novel domain responsible for forming the catalytic dimer in several class II RNRs. The 3D structure of the class II RNR from Rhodobacter sphaeroides reveals a so far undescribed α-helical domain in the dimer interface, which is embracing the other subunit. Genetic removal of this HUG domain leads to a severe reduction of activity paired with reduced dimerization capability. In comparison with other described RNRs, the enzyme with this domain is less dependent on the presence of nucleotides to act as allosteric effectors in the formation of dimers. The HUG domain appears to serve as an interlock to keep the dimer intact and functional even at low enzyme and/or effector concentrations.
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Affiliation(s)
- Tobias Fietze
- Chair of Molecular Biotechnology, Technische Universität Dresden, Dresden 01217, Germany
| | - Piotr Wilk
- Macromolecular Crystallography, Helmholtz-Zentrum Berlin, Berlin 12489, Germany.,Malopolska Centre of Biotechnology (MCB), Jagiellonian University, Krakow 31-007, Poland
| | - Florian Kabinger
- Department of Molecular Biology, Max Planck Institute for Multidisciplinary Sciences, Göttingen 37077, Germany
| | - Saber Anoosheh
- Department of Medical Biochemistry, Umeå University, Umeå 1965, Sweden
| | - Anders Hofer
- Department of Medical Biochemistry, Umeå University, Umeå 1965, Sweden
| | - Daniel Lundin
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm 114 19, Sweden
| | - Christian G Feiler
- Macromolecular Crystallography, Helmholtz-Zentrum Berlin, Berlin 12489, Germany
| | - Manfred S Weiss
- Macromolecular Crystallography, Helmholtz-Zentrum Berlin, Berlin 12489, Germany
| | - Christoph Loderer
- Chair of Molecular Biotechnology, Technische Universität Dresden, Dresden 01217, Germany
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4
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Levitz TS, Andree GA, Jonnalagadda R, Dawson CD, Bjork RE, Drennan CL. A rapid and sensitive assay for quantifying the activity of both aerobic and anaerobic ribonucleotide reductases acting upon any or all substrates. PLoS One 2022; 17:e0269572. [PMID: 35675376 PMCID: PMC9176816 DOI: 10.1371/journal.pone.0269572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 05/23/2022] [Indexed: 01/21/2023] Open
Abstract
Ribonucleotide reductases (RNRs) use radical-based chemistry to catalyze the conversion of all four ribonucleotides to deoxyribonucleotides. The ubiquitous nature of RNRs necessitates multiple RNR classes that differ from each other in terms of the phosphorylation state of the ribonucleotide substrates, oxygen tolerance, and the nature of both the metallocofactor employed and the reducing systems. Although these differences allow RNRs to produce deoxyribonucleotides needed for DNA biosynthesis under a wide range of environmental conditions, they also present a challenge for establishment of a universal activity assay. Additionally, many current RNR assays are limited in that they only follow the conversion of one ribonucleotide substrate at a time, but in the cell, all four ribonucleotides are actively being converted into deoxyribonucleotide products as dictated by the cellular concentrations of allosteric specificity effectors. Here, we present a liquid chromatography with tandem mass spectrometry (LC-MS/MS)-based assay that can determine the activity of both aerobic and anaerobic RNRs on any combination of substrates using any combination of allosteric effectors. We demonstrate that this assay generates activity data similar to past published results with the canonical Escherichia coli aerobic class Ia RNR. We also show that this assay can be used for an anaerobic class III RNR that employs formate as the reductant, i.e. Streptococcus thermophilus RNR. We further show that this class III RNR is allosterically regulated by dATP and ATP. Lastly, we present activity data for the simultaneous reduction of all four ribonucleotide substrates by the E. coli class Ia RNR under various combinations of allosteric specificity effectors. This validated LC-MS/MS assay is higher throughput and more versatile than the historically established radioactive activity and coupled RNR activity assays as well as a number of the published HPLC-based assays. The presented assay will allow for the study of a wide range of RNR enzymes under a wide range of conditions, facilitating the study of previously uncharacterized RNRs.
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Affiliation(s)
- Talya S. Levitz
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States of America
| | - Gisele A. Andree
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, United States of America
| | - Rohan Jonnalagadda
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States of America
| | - Christopher D. Dawson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States of America
| | - Rebekah E. Bjork
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, United States of America
| | - Catherine L. Drennan
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States of America,Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, United States of America,Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, United States of America,Center for Environmental Health Sciences, Massachusetts Institute of Technology, Cambridge, MA, United States of America,* E-mail:
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5
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McLean JT, Benny A, Nolan MD, Swinand G, Scanlan EM. Cysteinyl radicals in chemical synthesis and in nature. Chem Soc Rev 2021; 50:10857-10894. [PMID: 34397045 DOI: 10.1039/d1cs00254f] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Nature harnesses the unique properties of cysteinyl radical intermediates for a diverse range of essential biological transformations including DNA biosynthesis and repair, metabolism, and biological photochemistry. In parallel, the synthetic accessibility and redox chemistry of cysteinyl radicals renders them versatile reactive intermediates for use in a vast array of synthetic applications such as lipidation, glycosylation and fluorescent labelling of proteins, peptide macrocyclization and stapling, desulfurisation of peptides and proteins, and development of novel therapeutics. This review provides the reader with an overview of the role of cysteinyl radical intermediates in both chemical synthesis and biological systems, with a critical focus on mechanistic details. Direct insights from biological systems, where applied to chemical synthesis, are highlighted and potential avenues from nature which are yet to be explored synthetically are presented.
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Affiliation(s)
- Joshua T McLean
- Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse St., Dublin, D02 R590, Ireland.
| | - Alby Benny
- Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse St., Dublin, D02 R590, Ireland.
| | - Mark D Nolan
- Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse St., Dublin, D02 R590, Ireland.
| | - Glenna Swinand
- Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse St., Dublin, D02 R590, Ireland.
| | - Eoin M Scanlan
- Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse St., Dublin, D02 R590, Ireland.
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6
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Biotechnological and Biomedical Applications of Enzymes Involved in the Synthesis of Nucleosides and Nucleotides. Biomolecules 2021; 11:biom11081147. [PMID: 34439813 PMCID: PMC8393877 DOI: 10.3390/biom11081147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Accepted: 07/26/2021] [Indexed: 11/17/2022] Open
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7
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Schell E, Nouairia G, Steiner E, Weber N, Lundin D, Loderer C. Structural determinants and distribution of phosphate specificity in ribonucleotide reductases. J Biol Chem 2021; 297:101008. [PMID: 34314684 PMCID: PMC8365446 DOI: 10.1016/j.jbc.2021.101008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 07/21/2021] [Accepted: 07/23/2021] [Indexed: 11/24/2022] Open
Abstract
Ribonucleotide reductases (RNRs) catalyze the reduction of ribonucleotides to the corresponding deoxyribonucleotides, the building blocks of DNA. RNRs are specific for either ribonucleoside diphosphates or triphosphates as substrates. As far as is known, oxygen-dependent class I RNRs (NrdAB) all reduce ribonucleoside diphosphates, and oxygen-sensitive class III RNRs (NrdD) are all ribonucleoside triphosphate reducers, whereas the adenosylcobalamin-dependent class II (NrdJ) contains both ribonucleoside diphosphate and triphosphate reducers. However, it is unknown how this specificity is conveyed by the active site of the enzymes and how this feature developed in RNR evolution. By structural comparison of the active sites in different RNRs, we identified the apical loop of the phosphate-binding site as a potential structural determinant of substrate specificity. Grafting two residues from this loop from a diphosphate- to a triphosphate-specific RNR caused a change in preference from ribonucleoside triphosphate to diphosphate substrates in a class II model enzyme, confirming them as the structural determinants of phosphate specificity. The investigation of the phylogenetic distribution of this motif in class II RNRs yielded a likely monophyletic clade with the diphosphate-defining motif. This indicates a single evolutionary-split event early in NrdJ evolution in which diphosphate specificity developed from the earlier triphosphate specificity. For those interesting cases where organisms contain more than one nrdJ gene, we observed a preference for encoding enzymes with diverse phosphate specificities, suggesting that this varying phosphate specificity confers a selective advantage.
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Affiliation(s)
- Eugen Schell
- Institute for Microbiology, Technische Universität Dresden, Dresden, Saxony, Germany
| | - Ghada Nouairia
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Elisabeth Steiner
- Institute for Microbiology, Technische Universität Dresden, Dresden, Saxony, Germany
| | - Niclas Weber
- Institute for Microbiology, Technische Universität Dresden, Dresden, Saxony, Germany
| | - Daniel Lundin
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Christoph Loderer
- Institute for Microbiology, Technische Universität Dresden, Dresden, Saxony, Germany.
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8
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Frisch J, Maršić T, Loderer C. A Novel One-Pot Enzyme Cascade for the Biosynthesis of Cladribine Triphosphate. Biomolecules 2021; 11:biom11030346. [PMID: 33668847 PMCID: PMC7996316 DOI: 10.3390/biom11030346] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 02/19/2021] [Accepted: 02/22/2021] [Indexed: 02/06/2023] Open
Abstract
Cladribine triphosphate is the active compound of the anti-cancer and multiple sclerosis drug Mavenclad (cladribine). Biosynthesis of such non-natural deoxyribonucleotides is challenging but important in order to study the pharmaceutical modes of action. In this study, we developed a novel one-pot enzyme cascade for the biosynthesis of cladribine triphosphate, starting with the nucleobase 2Cl-adenine and the generic co-substrate phosphoribosyl pyrophosphate. The cascade is comprised of the three enzymes, namely, adenine phosphoribosyltransferase (APT), polyphosphate kinase (PPK), and ribonucleotide reductase (RNR). APT catalyzes the binding of the nucleobase to the ribose moiety, followed by two consecutive phosphorylation reactions by PPK. The formed nucleoside triphosphate is reduced to the final product 2Cl-deoxyadenonsine triphosphate (cladribine triphosphate) by the RNR. The cascade is feasible, showing comparative product concentrations and yields to existing enzyme cascades for nucleotide biosynthesis. While this study is limited to the biosynthesis of cladribine triphosphate, the design of the cascade offers the potential to extend its application to other important deoxyribonucleotides.
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Affiliation(s)
- Julia Frisch
- Chair for Molecular Biotechnology, Technical University, 01217 Dresden, Germany;
| | - Tin Maršić
- Laboratory for Genome Engineering and Synthetic Biology, Division of Biological Sciences, 4700 King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia;
| | - Christoph Loderer
- Chair for Molecular Biotechnology, Technical University, 01217 Dresden, Germany;
- Correspondence: ; Tel.: +49-351-463-39517
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9
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Loderer C, Holmfeldt K, Lundin D. Non-host class II ribonucleotide reductase in Thermus viruses: sequence adaptation and host interaction. PeerJ 2019; 7:e6700. [PMID: 30993041 PMCID: PMC6459318 DOI: 10.7717/peerj.6700] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 03/01/2019] [Indexed: 01/14/2023] Open
Abstract
Ribonucleotide reductases (RNR) are essential enzymes for all known life forms. Their current taxonomic distribution suggests extensive horizontal gene transfer e.g., by processes involving viruses. To improve our understanding of the underlying processes, we characterized a monomeric class II RNR (NrdJm) enzyme from a Thermus virus, a subclass not present in any sequenced Thermus spp. genome. Phylogenetic analysis revealed a distant origin of the nrdJm gene with the most closely related sequences found in mesophiles or moderate thermophiles from the Firmicutes phylum. GC-content, codon usage and the ratio of coding to non-coding substitutions (dN/dS) suggest extensive adaptation of the gene in the virus in terms of nucleotide composition and amino acid sequence. The NrdJm enzyme is a monomeric B12-dependent RNR with nucleoside triphosphate specificity. It exhibits a temperature optimum at 60–70 °C, which is in the range of the growth optimum of Thermus spp. Experiments in combination with the Thermus thermophilus thioredoxin system show that the enzyme is able to retrieve electrons from the host NADPH pool via host thioredoxin and thioredoxin reductases. This is different from other characterized viral RNRs such as T4 phage RNR, where a viral thioredoxin is present. We hence show that the monomeric class II RNR, present in Thermus viruses, was likely transferred from an organism phylogenetically distant from the one they were isolated from, and adapted to the new host in genetic signature and amino acids sequence.
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Affiliation(s)
- Christoph Loderer
- Institute for Microbiology, Technische Universität Dresden, Dresden, Saxony, Germany
| | - Karin Holmfeldt
- Centre for Ecology and Evolution in Microbial model Systems-EEMiS, Linnaeus University, Kalmar, Sweden
| | - Daniel Lundin
- Centre for Ecology and Evolution in Microbial model Systems-EEMiS, Linnaeus University, Kalmar, Sweden.,Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
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10
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Srinivas V, Lebrette H, Lundin D, Kutin Y, Sahlin M, Lerche M, Eirich J, Branca RMM, Cox N, Sjöberg BM, Högbom M. Metal-free ribonucleotide reduction powered by a DOPA radical in Mycoplasma pathogens. Nature 2018; 563:416-420. [PMID: 30429545 PMCID: PMC6317698 DOI: 10.1038/s41586-018-0653-6] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 08/22/2018] [Indexed: 12/14/2022]
Abstract
Ribonucleotide reductase (RNR) catalyses the only known de novo pathway for the production of all four deoxyribonucleotides that are required for DNA synthesis1,2. It is essential for all organisms that use DNA as their genetic material and is a current drug target3,4. Since the discovery that iron is required for function in the aerobic, class I RNR found in all eukaryotes and many bacteria, a dinuclear metal site has been viewed as necessary to generate and stabilize the catalytic radical that is essential for RNR activity5-7. Here we describe a group of RNR proteins in Mollicutes-including Mycoplasma pathogens-that possess a metal-independent stable radical residing on a modified tyrosyl residue. Structural, biochemical and spectroscopic characterization reveal a stable 3,4-dihydroxyphenylalanine (DOPA) radical species that directly supports ribonucleotide reduction in vitro and in vivo. This observation overturns the presumed requirement for a dinuclear metal site in aerobic ribonucleotide reductase. The metal-independent radical requires new mechanisms for radical generation and stabilization, processes that are targeted by RNR inhibitors. It is possible that this RNR variant provides an advantage under metal starvation induced by the immune system. Organisms that encode this type of RNR-some of which are developing resistance to antibiotics-are involved in diseases of the respiratory, urinary and genital tracts. Further characterization of this RNR family and its mechanism of cofactor generation will provide insight into new enzymatic chemistry and be of value in devising strategies to combat the pathogens that utilize it. We propose that this RNR subclass is denoted class Ie.
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Affiliation(s)
- Vivek Srinivas
- Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences, Stockholm, Sweden
| | - Hugo Lebrette
- Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences, Stockholm, Sweden
| | - Daniel Lundin
- Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences, Stockholm, Sweden
| | - Yuri Kutin
- Max Planck Institute for Chemical Energy Conversion, Mülheim an der Ruhr, Mülheim an der Ruhr, Germany
| | - Margareta Sahlin
- Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences, Stockholm, Sweden
| | - Michael Lerche
- Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences, Stockholm, Sweden
| | - Jürgen Eirich
- Cancer Proteomics Mass Spectrometry, Department of Oncology-Pathology, Science for Life Laboratory, Karolinska Institutet, Solna, Sweden
| | - Rui M M Branca
- Cancer Proteomics Mass Spectrometry, Department of Oncology-Pathology, Science for Life Laboratory, Karolinska Institutet, Solna, Sweden
| | - Nicholas Cox
- Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory, Australia
| | - Britt-Marie Sjöberg
- Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences, Stockholm, Sweden
| | - Martin Högbom
- Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences, Stockholm, Sweden.
- Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA.
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