1
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Song DY, Stubbe J, Nocera DG. Protein engineering a PhotoRNR chimera based on a unifying evolutionary apparatus among the natural classes of ribonucleotide reductases. Proc Natl Acad Sci U S A 2024; 121:e2317291121. [PMID: 38648489 PMCID: PMC11067019 DOI: 10.1073/pnas.2317291121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Accepted: 03/19/2024] [Indexed: 04/25/2024] Open
Abstract
Ribonucleotide reductases (RNRs) are essential enzymes that catalyze the de novo transformation of nucleoside 5'-di(tri)phosphates [ND(T)Ps, where N is A, U, C, or G] to their corresponding deoxynucleotides. Despite the diversity of factors required for function and the low sequence conservation across RNRs, a unifying apparatus consolidating RNR activity is explored. We combine aspects of the protein subunit simplicity of class II RNR with a modified version of Escherichia coli class la photoRNRs that initiate radical chemistry with light to engineer a mimic of a class II enzyme. The design of this RNR involves fusing a truncated form of the active site containing α subunit with the functionally important C-terminal tail of the radical-generating β subunit to render a chimeric RNR. Inspired by a recent cryo-EM structure, a [Re] photooxidant is located adjacent to Y356[β], which is an essential component of the radical transport pathway in class I RNRs. Combination of this RNR photochimera with cytidine diphosphate (CDP), adenosine triphosphate (ATP), and light resulted in the generation of Y356• along with production of deoxycytidine diphosphate (dCDP) and cytosine. The photoproducts reflect an active site chemistry consistent with both the consensus mechanism of RNR and chemistry observed when RNR is inactivated by mechanism-based inhibitors in the active site. The enzymatic activity of the RNR photochimera in the absence of any β metallocofactor highlights the adaptability of the 10-stranded αβ barrel finger loop to support deoxynucleotide formation and accommodate the design of engineered RNRs.
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Affiliation(s)
- David Y. Song
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA02138
| | - JoAnne Stubbe
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA02138
| | - Daniel G. Nocera
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA02138
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2
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Marques HM. The inorganic chemistry of the cobalt corrinoids - an update. J Inorg Biochem 2023; 242:112154. [PMID: 36871417 DOI: 10.1016/j.jinorgbio.2023.112154] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2023] [Revised: 01/23/2023] [Accepted: 01/26/2023] [Indexed: 02/05/2023]
Abstract
The inorganic chemistry of the cobalt corrinoids, derivatives of vitamin B12, is reviewed, with particular emphasis on equilibrium constants for, and kinetics of, their axial ligand substitution reactions. The role the corrin ligand plays in controlling and modifying the properties of the metal ion is emphasised. Other aspects of the chemistry of these compounds, including their structure, corrinoid complexes with metals other than cobalt, the redox chemistry of the cobalt corrinoids and their chemical redox reactions, and their photochemistry are discussed. Their role as catalysts in non-biological reactions and aspects of their organometallic chemistry are briefly mentioned. Particular mention is made of the role that computational methods - and especially DFT calculations - have played in developing our understanding of the inorganic chemistry of these compounds. A brief overview of the biological chemistry of the B12-dependent enzymes is also given for the reader's convenience.
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Affiliation(s)
- Helder M Marques
- Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand, Johannesburg 2050, South Africa.
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3
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Burnim AA, Spence MA, Xu D, Jackson CJ, Ando N. Comprehensive phylogenetic analysis of the ribonucleotide reductase family reveals an ancestral clade. eLife 2022; 11:79790. [PMID: 36047668 PMCID: PMC9531940 DOI: 10.7554/elife.79790] [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: 04/26/2022] [Accepted: 08/31/2022] [Indexed: 11/30/2022] Open
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. Here, we structurally aligned the diverse RNR family by the conserved catalytic barrel to reconstruct the first large-scale phylogeny consisting of 6779 sequences that unites all extant classes of the RNR family and performed evo-velocity analysis to independently validate our evolutionary model. With a robust phylogeny in-hand, we uncovered a novel, phylogenetically distinct clade that is placed as ancestral to the classes I and II RNRs, which we have termed clade Ø. We employed small-angle X-ray scattering (SAXS), cryogenic-electron microscopy (cryo-EM), and AlphaFold2 to investigate a member of this clade from Synechococcus phage S-CBP4 and report the most minimal RNR architecture to-date. Based on our analyses, we propose an evolutionary model of diversification in the RNR family and delineate how our phylogeny can be used as a roadmap for targeted future study. Billions of years ago, the Earth’s atmosphere had very little oxygen. It was only after some bacteria and early plants evolved to harness energy from sunlight that oxygen began to fill the Earth’s environment. Oxygen is highly reactive and can interfere with enzymes and other molecules that are essential to life. Organisms living at this point in history therefore had to adapt to survive in this new oxygen-rich world. An ancient family of enzymes known as ribonucleotide reductases are used by all free-living organisms and many viruses to repair and replicate their DNA. Because of their essential role in managing DNA, these enzymes have been around on Earth for billions of years. Understanding how they evolved could therefore shed light on how nature adapted to increasing oxygen levels and other environmental changes at the molecular level. One approach to study how proteins evolved is to use computational analysis to construct a phylogenetic tree. This reveals how existing members of a family are related to one another based on the chain of molecules (known as amino acids) that make up each protein. Despite having similar structures and all having the same function, ribonucleotide reductases have remarkably diverse sequences of amino acids. This makes it computationally very demanding to build a phylogenetic tree. To overcome this, Burnim, Spence, Xu et al. created a phylogenetic tree using structural information from a part of the enzyme that is relatively similar in many modern-day ribonucleotide reductases. The final result took seven continuous months on a supercomputer to generate, and includes over 6,000 members of the enzyme family. The phylogenetic tree revealed a new distinct group of ribonucleotide reductases that may explain how one adaptation to increasing levels of oxygen emerged in some family members, while another adaptation emerged in others. The approach used in this work also opens up a new way to study how other highly diverse enzymes and other protein families evolved, potentially revealing new insights about our planet’s past.
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Affiliation(s)
- Audrey A Burnim
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, United States
| | - Matthew A Spence
- Research School of Chemistry, Australian National University, Canberra, Australia
| | - Da Xu
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, United States
| | - Colin J Jackson
- Research School of Chemistry, Australian National University, Canberra, Australia
| | - Nozomi Ando
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, United States
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4
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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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5
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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: 1.0] [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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6
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Cobalamin is present in cells of non-tuberculous mycobacteria, but not in Mycobacterium tuberculosis. Sci Rep 2021; 11:12267. [PMID: 34112827 PMCID: PMC8192938 DOI: 10.1038/s41598-021-91430-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 05/26/2021] [Indexed: 01/22/2023] Open
Abstract
Cobalamin (vitamin B12) is a structurally complex molecule that acts as a cofactor for enzymes and regulates gene expression through so-called riboswitches. The existing literature on the vitamin B12 synthesis capacity in Mycobacterium tuberculosis is ambiguous, while in non-tuberculous mycobacteria (NTM) is rather marginal. Here we present the results of our investigation into the occurrence of vitamin B12 in mycobacteria. For detection purposes, immunoassay methods were applied to cell lysates of NTM and M. tuberculosis clinical and laboratory strains grown under different conditions. We show that whereas vitamin B12 is present in cells of various NTM species, it cannot be evidenced in strains of differently cultured M. tuberculosis, even though the genes responsible for vitamin B12 synthesis are actively expressed based on RNA-Seq data. In summary, we conclude that the production of vitamin B12 does occur in mycobacteria, with the likely exception of M. tuberculosis. Our results provide direct evidence of vitamin B12 synthesis in a clinically important group of bacteria.
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7
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Zhang S, Adrian L, Schüürmann G. Dehalococcoides-Mediated B 12-Dependent Reductive Dehalogenation of Aromatics Does Not Proceed through Outer-Sphere Electron Transfer. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:15751-15758. [PMID: 33237747 DOI: 10.1021/acs.est.0c04404] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Several anaerobic bacteria can couple the reduction of aromatic halides to energy conservation. This organohalide respiration is catalyzed by enzymes containing cob(I)alamin, an activated supernucleophilic form of the coenzyme vitamin B12. However, the mechanism underlying the electron transfer (inner-sphere vs outer-sphere ET) still remains elusive. To clarify this issue, we selected 36 fluoro-, chloro-, and bromobenzenes as representative substrates and calculated their free-energy barriers at the quantum chemical density functional theory level, considering a wide range of theoretically possible outer-sphere ET mechanisms. Across all 336 reaction routes addressed, 334 routes involve free-energy barriers larger than 20 kcal/mol. For two reaction routes with highly brominated benzenes, free-energy barriers below 20 kcal/mol imply abiotic reduction as observed in experiments. Thus, microbial B12-dependent aromatic reductive dehalogenation does not proceed through an outer-sphere ET mechanism. Instead, the present study strongly suggests that microbe-catalyzed reductive dehalogenation of aromatic halides is governed by inner-sphere ET.
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Affiliation(s)
- Shangwei Zhang
- Environmental Microbiomics Research Center, School of Environmental Science and Engineering, Guangdong Provincial Key Laboratory of Environmental Pollution Controol and Remediation Technology, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Sun Yat-Sen University, Guangzhou 510006, China
- UFZ Department of Ecological Chemistry, Helmholtz Centre for Environmental Research, Permoserstraße 15, 04318 Leipzig, Germany
| | - Lorenz Adrian
- UFZ Department of Environmental Biotechnology, Helmholtz Centre for Environmental Research, Permoserstraße 15, 04318 Leipzig, Germany
- Chair of Geobiotechnology, Technische Universität Berlin, Ackerstraße 76, 13355 Berlin, Germany
| | - Gerrit Schüürmann
- UFZ Department of Ecological Chemistry, Helmholtz Centre for Environmental Research, Permoserstraße 15, 04318 Leipzig, Germany
- Institute of Organic Chemistry, Technical University Bergakademie Freiberg, Leipziger Straße 29, 09596 Freiberg, Germany
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8
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Sokolovskaya OM, Mok KC, Park JD, Tran JLA, Quanstrom KA, Taga ME. Cofactor Selectivity in Methylmalonyl Coenzyme A Mutase, a Model Cobamide-Dependent Enzyme. mBio 2019; 10:e01303-19. [PMID: 31551329 PMCID: PMC6759758 DOI: 10.1128/mbio.01303-19] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 08/23/2019] [Indexed: 12/25/2022] Open
Abstract
Cobamides, a uniquely diverse family of enzyme cofactors related to vitamin B12, are produced exclusively by bacteria and archaea but used in all domains of life. While it is widely accepted that cobamide-dependent organisms require specific cobamides for their metabolism, the biochemical mechanisms that make cobamides functionally distinct are largely unknown. Here, we examine the effects of cobamide structural variation on a model cobamide-dependent enzyme, methylmalonyl coenzyme A (CoA) mutase (MCM). The in vitro binding affinity of MCM for cobamides can be dramatically influenced by small changes in the structure of the lower ligand of the cobamide, and binding selectivity differs between bacterial orthologs of MCM. In contrast, variations in the lower ligand have minor effects on MCM catalysis. Bacterial growth assays demonstrate that cobamide requirements of MCM in vitro largely correlate with in vivo cobamide dependence. This result underscores the importance of enzyme selectivity in the cobamide-dependent physiology of bacteria.IMPORTANCE Cobamides, including vitamin B12, are enzyme cofactors used by organisms in all domains of life. Cobamides are structurally diverse, and microbial growth and metabolism vary based on cobamide structure. Understanding cobamide preference in microorganisms is important given that cobamides are widely used and appear to mediate microbial interactions in host-associated and aquatic environments. Until now, the biochemical basis for cobamide preferences was largely unknown. In this study, we analyzed the effects of the structural diversity of cobamides on a model cobamide-dependent enzyme, methylmalonyl-CoA mutase (MCM). We found that very small changes in cobamide structure could dramatically affect the binding affinity of cobamides to MCM. Strikingly, cobamide-dependent growth of a model bacterium, Sinorhizobium meliloti, largely correlated with the cofactor binding selectivity of S. meliloti MCM, emphasizing the importance of cobamide-dependent enzyme selectivity in bacterial growth and cobamide-mediated microbial interactions.
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Affiliation(s)
- Olga M Sokolovskaya
- Department of Plant & Microbial Biology, University of California Berkeley, Berkeley, California, USA
- Department of Chemistry, University of California Berkeley, Berkeley, California, USA
| | - Kenny C Mok
- Department of Plant & Microbial Biology, University of California Berkeley, Berkeley, California, USA
| | - Jong Duk Park
- Department of Plant & Microbial Biology, University of California Berkeley, Berkeley, California, USA
| | - Jennifer L A Tran
- Department of Plant & Microbial Biology, University of California Berkeley, Berkeley, California, USA
| | - Kathryn A Quanstrom
- Department of Plant & Microbial Biology, University of California Berkeley, Berkeley, California, USA
| | - Michiko E Taga
- Department of Plant & Microbial Biology, University of California Berkeley, Berkeley, California, USA
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9
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Shibata N, Sueyoshi Y, Higuchi Y, Toraya T. Direct Participation of a Peripheral Side Chain of a Corrin Ring in Coenzyme B12
Catalysis. Angew Chem Int Ed Engl 2018; 57:7830-7835. [DOI: 10.1002/anie.201803591] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2018] [Indexed: 11/08/2022]
Affiliation(s)
- Naoki Shibata
- Department of Picobiology/Life Science; Graduate School of Life Science; University of Hyogo; 3-2-1 Koto Kamigori-cho, Ako-gun Hyogo 678-1297 Japan
- The RIKEN SPring-8 Center; 1-1-1 Koto Sayo-cho, Sato-gun Hyogo 678-5248 Japan
| | - Yui Sueyoshi
- Department of Picobiology/Life Science; Graduate School of Life Science; University of Hyogo; 3-2-1 Koto Kamigori-cho, Ako-gun Hyogo 678-1297 Japan
| | - Yoshiki Higuchi
- Department of Picobiology/Life Science; Graduate School of Life Science; University of Hyogo; 3-2-1 Koto Kamigori-cho, Ako-gun Hyogo 678-1297 Japan
- The RIKEN SPring-8 Center; 1-1-1 Koto Sayo-cho, Sato-gun Hyogo 678-5248 Japan
| | - Tetsuo Toraya
- Department of Bioscience and Biotechnology; Graduate School of Natural Science and Technology; Okayama University; Tsushima-naka Okayama 700-8530 Japan
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10
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Shibata N, Sueyoshi Y, Higuchi Y, Toraya T. Direct Participation of a Peripheral Side Chain of a Corrin Ring in Coenzyme B12
Catalysis. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201803591] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Naoki Shibata
- Department of Picobiology/Life Science; Graduate School of Life Science; University of Hyogo; 3-2-1 Koto Kamigori-cho, Ako-gun Hyogo 678-1297 Japan
- The RIKEN SPring-8 Center; 1-1-1 Koto Sayo-cho, Sato-gun Hyogo 678-5248 Japan
| | - Yui Sueyoshi
- Department of Picobiology/Life Science; Graduate School of Life Science; University of Hyogo; 3-2-1 Koto Kamigori-cho, Ako-gun Hyogo 678-1297 Japan
| | - Yoshiki Higuchi
- Department of Picobiology/Life Science; Graduate School of Life Science; University of Hyogo; 3-2-1 Koto Kamigori-cho, Ako-gun Hyogo 678-1297 Japan
- The RIKEN SPring-8 Center; 1-1-1 Koto Sayo-cho, Sato-gun Hyogo 678-5248 Japan
| | - Tetsuo Toraya
- Department of Bioscience and Biotechnology; Graduate School of Natural Science and Technology; Okayama University; Tsushima-naka Okayama 700-8530 Japan
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11
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Alnajar S, Khadka B, Gupta RS. Ribonucleotide Reductases from Bifidobacteria Contain Multiple Conserved Indels Distinguishing Them from All Other Organisms: In Silico Analysis of the Possible Role of a 43 aa Bifidobacteria-Specific Insert in the Class III RNR Homolog. Front Microbiol 2017; 8:1409. [PMID: 28824557 PMCID: PMC5535262 DOI: 10.3389/fmicb.2017.01409] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2017] [Accepted: 07/11/2017] [Indexed: 01/05/2023] Open
Abstract
Bifidobacteria comprises an important group/order of bacteria whose members have widespread usage in the food and health industry due to their health-promoting activity in the human gastrointestinal tract. However, little is known about the underlying molecular properties that are responsible for the probiotic effects of these bacteria. The enzyme ribonucleotide reductase (RNR) plays a key role in all organisms by reducing nucleoside di- or tri- phosphates into corresponding deoxyribose derivatives required for DNA synthesis, and RNR homologs belonging to classes I and III are present in either most or all Bifidobacteriales. Comparative analyses of these RNR homologs have identified several novel sequence features in the forms of conserved signature indels (CSIs) that are exclusively found in bifidobacterial RNRs. Specifically, in the large subunit of the aerobic class Ib RNR, three CSIs have been identified that are uniquely found in the Bifidobacteriales homologs. Similarly, the large subunit of the anaerobic class III RNR contains five CSIs that are also distinctive characteristics of bifidobacteria. Phylogenetic analyses indicate that these CSIs were introduced in a common ancestor of the Bifidobacteriales and retained by all descendants, likely due to their conferring advantageous functional roles. The identified CSIs in the bifidobacterial RNR homologs provide useful tools for further exploration of the novel functional aspects of these important enzymes that are exclusive to these bacteria. We also report here the results of homology modeling studies, which indicate that most of the bifidobacteria-specific CSIs are located within the surface loops of the RNRs, and of these, a large 43 amino acid insert in the class III RNR homolog forms an extension of the allosteric regulatory site known to be essential for protein function. Preliminary docking studies suggest that this large CSI may be playing a role in enhancing the stability of the RNR dimer complex. The possible significances of the identified CSIs, as well as the distribution of RNR homologs in the Bifidobacteriales, are discussed.
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Affiliation(s)
- Seema Alnajar
- Department of Biochemistry and Biomedical Sciences, McMaster University, HamiltonON, Canada
| | - Bijendra Khadka
- Department of Biochemistry and Biomedical Sciences, McMaster University, HamiltonON, Canada
| | - Radhey S Gupta
- Department of Biochemistry and Biomedical Sciences, McMaster University, HamiltonON, Canada
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12
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Prieto L, Neuburger M, Spingler B, Zelder F. Inorganic Cyanide as Protecting Group in the Stereospecific Reconstitution of Vitamin B12 from an Artificial Green Secocorrinoid. Org Lett 2016; 18:5292-5295. [DOI: 10.1021/acs.orglett.6b02611] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Lucas Prieto
- Department
of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Markus Neuburger
- Department
of Chemistry, University of Basel, Spitalstr. 51, CH 4056 Basel, Switzerland
| | - Bernhard Spingler
- Department
of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
| | - Felix Zelder
- Department
of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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13
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Park K, Mera PE, Escalante-Semerena JC, Brunold TC. Resonance Raman spectroscopic study of the interaction between Co(II)rrinoids and the ATP:corrinoid adenosyltransferase PduO from Lactobacillus reuteri. J Biol Inorg Chem 2016; 21:669-81. [PMID: 27383231 PMCID: PMC5118822 DOI: 10.1007/s00775-016-1371-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Accepted: 06/14/2016] [Indexed: 12/01/2022]
Abstract
The human-type ATP:corrinoid adenosyltransferase PduO from Lactobacillus reuteri (LrPduO) catalyzes the adenosylation of Co(II)rrinoids to generate adenosylcobalamin (AdoCbl) or adenosylcobinamide (AdoCbi(+)). This process requires the formation of "supernucleophilic" Co(I)rrinoid intermediates in the enzyme active site which are properly positioned to abstract the adeonsyl moiety from co-substrate ATP. Previous magnetic circular dichroism (MCD) spectroscopic and X-ray crystallographic analyses revealed that LrPduO achieves the thermodynamically challenging reduction of Co(II)rrinoids by displacing the axial ligand with a non-coordinating phenylalanine residue to produce a four-coordinate species. However, relatively little is currently known about the interaction between the tetradentate equatorial ligand of Co(II)rrinoids (the corrin ring) and the enzyme active site. To address this issue, we have collected resonance Raman (rR) data of Co(II)rrinoids free in solution and bound to the LrPduO active site. The relevant resonance-enhanced vibrational features of the free Co(II)rrinoids are assigned on the basis of rR intensity calculations using density functional theory to establish a suitable framework for interpreting rR spectral changes that occur upon Co(II)rrinoid binding to the LrPduO/ATP complex in terms of structural perturbations of the corrin ring. To complement our rR data, we have also obtained MCD spectra of Co(II)rrinoids bound to LrPduO complexed with the ATP analogue UTP. Collectively, our results provide compelling evidence that in the LrPduO active site, the corrin ring of Co(II)rrinoids is firmly locked in place by several amino acid side chains so as to facilitate the dissociation of the axial ligand.
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Affiliation(s)
- Kiyoung Park
- Department of Chemistry, Korea Advanced Institute of Science and Technology, Yuseong-gu, Daejeon, 34141, Republic of Korea.
| | - Paola E Mera
- Department of Chemistry and Biochemistry, New Mexico State University, Las Cruces, NM, 88003, USA
| | | | - Thomas C Brunold
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706, USA.
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14
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Zelder F. Recent trends in the development of vitamin B12 derivatives for medicinal applications. Chem Commun (Camb) 2015; 51:14004-17. [PMID: 26287029 DOI: 10.1039/c5cc04843e] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
This Feature Article highlights recent developments in the field of vitamin B12 derivatives for medicinal applications. The following topics are emphasized: (1) the development of aquacorrinoids for cyanide detection and detoxification, (2) the use of vitamin B12 conjugates and (3) antivitamins B12 for therapy and diagnosis, and (4) the design of corrinoids as activators of soluble guanylyl cyclase (sGC).
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Affiliation(s)
- Felix Zelder
- Department of Chemistry, University of Zürich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland.
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15
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Shibata N, Toraya T. Molecular architectures and functions of radical enzymes and their (re)activating proteins. J Biochem 2015; 158:271-92. [PMID: 26261050 DOI: 10.1093/jb/mvv078] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 07/22/2015] [Indexed: 02/07/2023] Open
Abstract
Certain proteins utilize the high reactivity of radicals for catalysing chemically challenging reactions. These proteins contain or form a radical and therefore named 'radical enzymes'. Radicals are introduced by enzymes themselves or by (re)activating proteins called (re)activases. The X-ray structures of radical enzymes and their (re)activases revealed some structural features of these molecular apparatuses which solved common enigmas of radical enzymes—i.e. how the enzymes form or introduce radicals at the active sites, how they use the high reactivity of radicals for catalysis, how they suppress undesired side reactions of highly reactive radicals and how they are (re)activated when inactivated by extinction of radicals. This review highlights molecular architectures of radical B12 enzymes, radical SAM enzymes, tyrosyl radical enzymes, glycyl radical enzymes and their (re)activating proteins that support their functions. For generalization, comparisons of the recently reported structures of radical enzymes with those of canonical radical enzymes are summarized here.
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Affiliation(s)
- Naoki Shibata
- Department of Life Science, Graduate School of Life Science, University of Hyogo, 3-2-1 Koto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan and
| | - Tetsuo Toraya
- Department of Bioscience and Biotechnology, Graduate School of Natural Science and Technology, Okayama University, Tsushima-naka, Kita-ku, Okayama 700-8530, Japan
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16
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Crona M, Hofer A, Astorga-Wells J, Sjöberg BM, Tholander F. Biochemical Characterization of the Split Class II Ribonucleotide Reductase from Pseudomonas aeruginosa. PLoS One 2015. [PMID: 26225432 PMCID: PMC4520616 DOI: 10.1371/journal.pone.0134293] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The opportunistic pathogen Pseudomonas aeruginosa can grow under both aerobic and anaerobic conditions. Its flexibility with respect to oxygen load is reflected by the fact that its genome encodes all three existing classes of ribonucleotides reductase (RNR): the oxygen-dependent class I RNR, the oxygen-indifferent class II RNR, and the oxygen-sensitive class III RNR. The P. aeruginosa class II RNR is expressed as two separate polypeptides (NrdJa and NrdJb), a unique example of a split RNR enzyme in a free-living organism. A split class II RNR is also found in a few closely related γ-Proteobacteria. We have characterized the P. aeruginosa class II RNR and show that both subunits are required for formation of a biologically functional enzyme that can sustain vitamin B12-dependent growth. Binding of the B12 coenzyme as well as substrate and allosteric effectors resides in the NrdJa subunit, whereas the NrdJb subunit mediates efficient reductive dithiol exchange during catalysis. A combination of activity assays and activity-independent methods like surface plasmon resonance and gas phase electrophoretic macromolecule analysis suggests that the enzymatically active form of the enzyme is a (NrdJa-NrdJb)2 homodimer of heterodimers, and a combination of hydrogen-deuterium exchange experiments and molecular modeling suggests a plausible region in NrdJa that interacts with NrdJb. Our detailed characterization of the split NrdJ from P. aeruginosa provides insight into the biochemical function of a unique enzyme known to have central roles in biofilm formation and anaerobic growth.
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Affiliation(s)
- Mikael Crona
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Scheeles väg 2, SE-17177, Stockholm, Sweden
| | - Anders Hofer
- Department of Medical Biochemistry and Biophysics, Umeå University, SE-90187, Umeå, Sweden
| | - Juan Astorga-Wells
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Scheeles väg 2, SE-17177, Stockholm, Sweden
| | - Britt-Marie Sjöberg
- Department of Biochemistry and Biophysics, Stockholm University, SE-10691, Stockholm, Sweden
| | - Fredrik Tholander
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Scheeles väg 2, SE-17177, Stockholm, Sweden
- * E-mail:
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17
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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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18
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Torrents E. Ribonucleotide reductases: essential enzymes for bacterial life. Front Cell Infect Microbiol 2014; 4:52. [PMID: 24809024 PMCID: PMC4009431 DOI: 10.3389/fcimb.2014.00052] [Citation(s) in RCA: 138] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Accepted: 04/08/2014] [Indexed: 11/13/2022] Open
Abstract
Ribonucleotide reductase (RNR) is a key enzyme that mediates the synthesis of deoxyribonucleotides, the DNA precursors, for DNA synthesis in every living cell. This enzyme converts ribonucleotides to deoxyribonucleotides, the building blocks for DNA replication, and repair. Clearly, RNR enzymes have contributed to the appearance of genetic material that exists today, being essential for the evolution of all organisms on Earth. The strict control of RNR activity and dNTP pool sizes is important, as pool imbalances increase mutation rates, replication anomalies, and genome instability. Thus, RNR activity should be finely regulated allosterically and at the transcriptional level. In this review we examine the distribution, the evolution, and the genetic regulation of bacterial RNRs. Moreover, this enzyme can be considered an ideal target for anti-proliferative compounds designed to inhibit cell replication in eukaryotic cells (cancer cells), parasites, viruses, and bacteria.
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Affiliation(s)
- Eduard Torrents
- Bacterial Infections and Antimicrobial Therapies Group, Institute for Bioengineering of Catalonia Barcelona, Spain
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19
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Zelder F, Zhou K, Sonnay M. Peptide B12: emerging trends at the interface of inorganic chemistry, chemical biology and medicine. Dalton Trans 2013; 42:854-62. [PMID: 23160417 DOI: 10.1039/c2dt32005c] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The sophisticated and efficient delivery of vitamin B(12) ("B(12)") into cells offers promise for B(12)-bioconjugates in medicinal diagnosis and therapy. It is therefore surprising that rather little attention is presently paid to an alternative strategy in drug design: the development of structurally perfect, but catalytically inactive semi-artificial B(12) surrogates. Vitamin B(12) cofactors catalyse important biological transformations and are indispensible for humans and most other forms of life. This strong metabolic dependency exhibits enormous medicinal opportunities. Inhibitors of B(12) dependent enzymes are potential suppressors of fast proliferating cancer cells. This perspective article focuses on the design and study of backbone modified B(12) derivatives, particularly on peptide B(12) derivatives. Peptide B(12) is a recently introduced class of biomimetic cobalamins bearing an artificial peptide backbone with adjustable coordination and redox-properties. Pioneering biological studies demonstrated reduced catalytic activity, combined with inhibitory potential that is encouraging for future efforts in turning natural cofactors into new anti-proliferative agents.
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Affiliation(s)
- Felix Zelder
- Institute of Inorganic Chemistry, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
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20
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Dowling DP, Croft AK, Drennan CL. Radical use of Rossmann and TIM barrel architectures for controlling coenzyme B12 chemistry. Annu Rev Biophys 2013; 41:403-27. [PMID: 22577824 DOI: 10.1146/annurev-biophys-050511-102225] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The ability of enzymes to harness free-radical chemistry allows for some of the most amazing transformations in nature, including reduction of ribonucleotides and carbon skeleton rearrangements. Enzyme cofactors involved in this chemistry can be large and complex, such as adenosylcobalamin (coenzyme B(12)), simpler, such as S-adenosylmethionine and an iron-sulfur cluster (i.e., poor man's B(12)), or very small, such as one nonheme iron atom coordinated by protein ligands. Although the chemistry catalyzed by these enzyme-bound cofactors is unparalleled, it does come at a price. The enzyme must be able to control these radical reactions, preventing unwanted chemistry and protecting the enzyme active site from damage. Here, we consider a set of radical folds: the (β/α)(8) or TIM barrel, combined with a Rossmann domain for coenzyme B(12)-dependent chemistry. Using specific enzyme examples, we consider how nature employs the common TIM barrel fold and its Rossmann domain partner for radical-based chemistry.
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Affiliation(s)
- Daniel P Dowling
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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21
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Sukumar N. Crystallographic studies on B12 binding proteins in eukaryotes and prokaryotes. Biochimie 2013; 95:976-88. [PMID: 23395752 DOI: 10.1016/j.biochi.2013.01.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2012] [Accepted: 01/28/2013] [Indexed: 01/22/2023]
Abstract
The X-ray crystal structures of several important vitamin B12 binding proteins that have been solved in recent years have enhanced our current understanding in the vitamin B12 field. These structurally diverse groups of B12 binding proteins perform various important biological activities, both by transporting B12 as well as catalyzing various biological reactions. An in-depth comparative analysis of these structures was carried out using PDB coordinates of a carefully chosen database of B12 binding proteins to correlate the overall folding of the molecule with phylogeny, the B12 interactions, and with their biological function. The structures of these proteins are discussed in the context of this comparative analysis.
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Affiliation(s)
- Narayanasami Sukumar
- NE-CAT and Department of Chemistry and Chemical Biology, Cornell University, Building 436E, Argonne National Laboratory, Argonne, IL 60439, USA.
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22
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Makins C, Pickering AV, Mariani C, Wolthers KR. Mutagenesis of a conserved glutamate reveals the contribution of electrostatic energy to adenosylcobalamin co-C bond homolysis in ornithine 4,5-aminomutase and methylmalonyl-CoA mutase. Biochemistry 2013; 52:878-88. [PMID: 23311430 DOI: 10.1021/bi3012719] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Binding of substrate to ornithine 4,5-aminomutase (OAM) and methylmalonyl-CoA mutase (MCM) leads to the formation of an electrostatic interaction between a conserved glutamate side chain and the adenosyl ribose of the adenosylcobalamin (AdoCbl) cofactor. The contribution of this residue (Glu338 in OAM from Clostridium sticklandii and Glu392 in human MCM) to AdoCbl Co-C bond labilization and catalysis was evaluated by substituting the residue with a glutamine, aspartate, or alanine. The OAM variants, E338Q, E338D, and E338A, showed 90-, 380-, and 670-fold reductions in catalytic turnover and 20-, 60-, and 220-fold reductions in k(cat)/K(m), respectively. Likewise, the MCM variants, E392Q, E392D, and E392A, showed 16-, 330-, and 12-fold reductions in k(cat), respectively. Binding of substrate to OAM is unaffected by the single-amino acid mutation as stopped-flow absorbance spectroscopy showed that the rates of external aldimine formation in the OAM variants were similar to that of the native enzyme. The decrease in the level of catalysis is instead linked to impaired Co-C bond rupture, as UV-visible spectroscopy did not show detectable AdoCbl homolysis upon binding of the physiological substrate, d-ornithine. AdoCbl homolysis was also not detected in the MCM mutants, as it was for the native enzyme. We conclude from these results that a gradual weakening of the electrostatic energy between the protein and the ribose leads to a progressive increase in the activation energy barrier for Co-C bond homolysis, thereby pointing to a key role for the conserved polar glutamate residue in controlling the initial generation of radical species.
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Affiliation(s)
- Caitlyn Makins
- Department of Chemistry, University of British Columbia, 3333 University Way, Kelowna, BC, Canada
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23
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Dowling DP, Vey JL, Croft AK, Drennan CL. Structural diversity in the AdoMet radical enzyme superfamily. BIOCHIMICA ET BIOPHYSICA ACTA 2012; 1824:1178-95. [PMID: 22579873 PMCID: PMC3523193 DOI: 10.1016/j.bbapap.2012.04.006] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Revised: 04/04/2012] [Accepted: 04/19/2012] [Indexed: 11/18/2022]
Abstract
AdoMet radical enzymes are involved in processes such as cofactor biosynthesis, anaerobic metabolism, and natural product biosynthesis. These enzymes utilize the reductive cleavage of S-adenosylmethionine (AdoMet) to afford l-methionine and a transient 5'-deoxyadenosyl radical, which subsequently generates a substrate radical species. By harnessing radical reactivity, the AdoMet radical enzyme superfamily is responsible for an incredible diversity of chemical transformations. Structural analysis reveals that family members adopt a full or partial Triose-phosphate Isomerase Mutase (TIM) barrel protein fold, containing core motifs responsible for binding a catalytic [4Fe-4S] cluster and AdoMet. Here we evaluate over twenty structures of AdoMet radical enzymes and classify them into two categories: 'traditional' and 'ThiC-like' (named for the structure of 4-amino-5-hydroxymethyl-2-methylpyrimidine phosphate synthase (ThiC)). In light of new structural data, we reexamine the 'traditional' structural motifs responsible for binding the [4Fe-4S] cluster and AdoMet, and compare and contrast these motifs with the ThiC case. We also review how structural data combine with biochemical, spectroscopic, and computational data to help us understand key features of this enzyme superfamily, such as the energetics, the triggering, and the molecular mechanisms of AdoMet reductive cleavage. This article is part of a Special Issue entitled: Radical SAM Enzymes and Radical Enzymology.
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Affiliation(s)
- Daniel P. Dowling
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Jessica L. Vey
- Department of Chemistry and Biochemistry, California State University Northridge, Northridge, CA 91330-8262
| | - Anna K. Croft
- School of Chemistry, University of Wales Bangor, Bangor, Gwynedd LL57 2UW, UK
| | - Catherine L. Drennan
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
- Departments of Chemistry and Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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24
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Zhou K, Oetterli RM, Brandl H, Lyatuu FE, Buckel W, Zelder F. Chemistry and Bioactivity of an Artificial Adenosylpeptide B12Cofactor. Chembiochem 2012; 13:2052-5. [DOI: 10.1002/cbic.201200429] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2012] [Indexed: 02/05/2023]
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25
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Froese DS, Krojer T, Wu X, Shrestha R, Kiyani W, von Delft F, Gravel RA, Oppermann U, Yue WW. Structure of MMACHC Reveals an Arginine-Rich Pocket and a Domain-Swapped Dimer for Its B12 Processing Function. Biochemistry 2012; 51:5083-90. [DOI: 10.1021/bi300150y] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | | | - Xuchu Wu
- Department of Biochemistry & Molecular Biology, University of Calgary, Calgary, Canada
| | | | | | | | - Roy A. Gravel
- Department of Biochemistry & Molecular Biology, University of Calgary, Calgary, Canada
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26
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Abstract
Ribonucleotide reductase (RNR) is the only source for de novo production of the four deoxyribonucleoside triphosphate (dNTP) building blocks needed for DNA synthesis and repair. It is crucial that these dNTP pools are carefully balanced, since mutation rates increase when dNTP levels are either unbalanced or elevated. RNR is the major player in this homeostasis, and with its four different substrates, four different allosteric effectors and two different effector binding sites, it has one of the most sophisticated allosteric regulations known today. In the past few years, the structures of RNRs from several bacteria, yeast and man have been determined in the presence of allosteric effectors and substrates, revealing new information about the mechanisms behind the allosteric regulation. A common theme for all studied RNRs is a flexible loop that mediates modulatory effects from the allosteric specificity site (s-site) to the catalytic site for discrimination between the four substrates. Much less is known about the allosteric activity site (a-site), which functions as an on-off switch for the enzyme's overall activity by binding ATP (activator) or dATP (inhibitor). The two nucleotides induce formation of different enzyme oligomers, and a recent structure of a dATP-inhibited α(6)β(2) complex from yeast suggested how its subunits interacted non-productively. Interestingly, the oligomers formed and the details of their allosteric regulation differ between eukaryotes and Escherichia coli. Nevertheless, these differences serve a common purpose in an essential enzyme whose allosteric regulation might date back to the era when the molecular mechanisms behind the central dogma evolved.
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Affiliation(s)
- Anders Hofer
- Department of Medical Biochemistry and Biophysics, Umeå University, Umeå, Sweden.
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27
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Targeting the Large Subunit of Human Ribonucleotide Reductase for Cancer Chemotherapy. Pharmaceuticals (Basel) 2011; 4:1328-1354. [PMID: 23115527 PMCID: PMC3483043 DOI: 10.3390/ph4101328] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Ribonucleotide reductase (RR) is a crucial enzyme in de novo DNA synthesis, where it catalyses the rate determining step of dNTP synthesis. RRs consist of a large subunit called RR1 (α), that contains two allosteric sites and one catalytic site, and a small subunit called RR2 (β), which houses a tyrosyl free radical essential for initiating catalysis. The active form of mammalian RR is an αnβm hetero oligomer. RR inhibitors are cytotoxic to proliferating cancer cells. In this brief review we will discuss the three classes of RR, the catalytic mechanism of RR, the regulation of the dNTP pool, the substrate selection, the allosteric activation, inactivation by ATP and dATP, and the nucleoside drugs that target RR. We will also discuss possible strategies for developing a new class of drugs that disrupts the RR assembly.
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28
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Gruber K, Puffer B, Kräutler B. Vitamin B12-derivatives-enzyme cofactors and ligands of proteins and nucleic acids. Chem Soc Rev 2011; 40:4346-63. [PMID: 21687905 DOI: 10.1039/c1cs15118e] [Citation(s) in RCA: 190] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
B(12)-cofactors play important roles in the metabolism of microorganisms, animals and humans. Microorganisms are the only natural sources of B(12)-derivatives, and the latter are "vitamins" for other B(12)-requiring organisms. Some B(12)-dependent enzymes catalyze complex isomerisation reactions, such as methylmalonyl-CoA mutase. They need coenzyme B(12), an organometallic B(12)-derivative, to induce enzymatic radical reactions. Another group of widely relevant enzymes catalyzes the transfer of methyl groups, such as methionine synthase, which uses methylcobalamin as cofactor. This tutorial review covers structure and reactivity of B(12)-derivatives and structural aspects of their interactions with proteins and nucleotides, which are crucial for the efficient catalysis by the important B(12)-dependent enzymes, and for achieving and regulating uptake and transport of B(12)-derivatives.
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Affiliation(s)
- Karl Gruber
- Institute of Molecular Biosciences, University of Graz, Humboldtstr. 50/3, Graz, A-8010, Austria
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29
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30
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Högbom M. Metal use in ribonucleotide reductase R2, di-iron, di-manganese and heterodinuclear—an intricate bioinorganic workaround to use different metals for the same reaction. Metallomics 2011; 3:110-20. [DOI: 10.1039/c0mt00095g] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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31
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Zelenka K, Brandl H, Spingler B, Zelder F. Coordination chemistry and biological activity of 5′-OH modified quinoline–B12 derivatives. Dalton Trans 2011; 40:9665-7. [DOI: 10.1039/c1dt11161b] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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