1
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Greenberg HC, Majumdar A, Cheema EK, Kozyryev A, Rokita SE. 19F NMR Reveals the Dynamics of Substrate Binding and Lid Closure for Iodotyrosine Deiodinase as a Complement to Steady-State Kinetics and Crystallography. Biochemistry 2024. [PMID: 39137127 DOI: 10.1021/acs.biochem.4c00243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/15/2024]
Abstract
Active site lids are common features of enzymes and typically undergo conformational changes upon substrate binding to promote catalysis. Iodotyrosine deiodinase is no exception and contains a lid segment in all of its homologues from human to bacteria. The solution-state dynamics of the lid have now been characterized using 19F NMR spectroscopy with a CF3-labeled enzyme and CF3O-labeled ligands. From two-dimensional 19F-19F NMR exchange spectroscopy, interconversion rates between the free and bound states of a CF3O-substituted tyrosine (45 ± 10 s-1) and the protein label (40 ± 3 s-1) are very similar and suggest a correlation between ligand binding and conformational reorganization of the lid. Both occur at rates that are ∼100-fold faster than turnover, and therefore these steps do not limit catalysis. A simple CF3O-labeled phenol also binds to the active site and induces a conformational change in the lid segment that was not previously detectable by crystallography. Exchange rates of the ligand (130 ± 20 s-1) and protein (98 ± 8 s-1) in this example are faster than those above but remain self-consistent to affirm a correlation between ordering of the lid and binding of the ligand. Both ligands also protect the protein from limited proteolysis, as expected from their ability to stabilize a compact lid structure. However, the minimal turnover of simple phenol substrates indicates that such stabilization may be necessary but is not sufficient for efficient catalysis.
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Affiliation(s)
- Harrison C Greenberg
- Chemistry-Biology Interface Graduate Training Program, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
| | - Ananya Majumdar
- Biomolecular NMR Center, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
| | - Ekroop Kaur Cheema
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
| | - Anton Kozyryev
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
| | - Steven E Rokita
- Chemistry-Biology Interface Graduate Training Program, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, United States
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2
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Su Q, Xu B, Chen X, Rokita SE. Misregulation of bromotyrosine compromises fertility in male Drosophila. Proc Natl Acad Sci U S A 2024; 121:e2322501121. [PMID: 38748578 PMCID: PMC11126969 DOI: 10.1073/pnas.2322501121] [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: 01/02/2024] [Accepted: 04/15/2024] [Indexed: 05/27/2024] Open
Abstract
Biological regulation often depends on reversible reactions such as phosphorylation, acylation, methylation, and glycosylation, but rarely halogenation. A notable exception is the iodination and deiodination of thyroid hormones. Here, we report detection of bromotyrosine and its subsequent debromination during Drosophila spermatogenesis. Bromotyrosine is not evident when Drosophila express a native flavin-dependent dehalogenase that is homologous to the enzyme responsible for iodide salvage from iodotyrosine in mammals. Deletion or suppression of the dehalogenase-encoding condet (cdt) gene in Drosophila allows bromotyrosine to accumulate with no detectable chloro- or iodotyrosine. The presence of bromotyrosine in the cdt mutant males disrupts sperm individualization and results in decreased fertility. Transgenic expression of the cdt gene in late-staged germ cells rescues this defect and enhances tolerance of male flies to bromotyrosine. These results are consistent with reversible halogenation affecting Drosophila spermatogenesis in a process that had previously eluded metabolomic, proteomic, and genomic analyses.
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Affiliation(s)
- Qi Su
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD21218
| | - Bing Xu
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD21218
| | - Xin Chen
- HHMI, The Johns Hopkins University, Baltimore, MD21218
- Department of Biology, The Johns Hopkins University, Baltimore, MD21218
| | - Steven E. Rokita
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD21218
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3
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Patel KD, MacDonald MR, Ahmed SF, Singh J, Gulick AM. Structural advances toward understanding the catalytic activity and conformational dynamics of modular nonribosomal peptide synthetases. Nat Prod Rep 2023; 40:1550-1582. [PMID: 37114973 PMCID: PMC10510592 DOI: 10.1039/d3np00003f] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Indexed: 04/29/2023]
Abstract
Covering: up to fall 2022.Nonribosomal peptide synthetases (NRPSs) are a family of modular, multidomain enzymes that catalyze the biosynthesis of important peptide natural products, including antibiotics, siderophores, and molecules with other biological activity. The NRPS architecture involves an assembly line strategy that tethers amino acid building blocks and the growing peptides to integrated carrier protein domains that migrate between different catalytic domains for peptide bond formation and other chemical modifications. Examination of the structures of individual domains and larger multidomain proteins has identified conserved conformational states within a single module that are adopted by NRPS modules to carry out a coordinated biosynthetic strategy that is shared by diverse systems. In contrast, interactions between modules are much more dynamic and do not yet suggest conserved conformational states between modules. Here we describe the structures of NRPS protein domains and modules and discuss the implications for future natural product discovery.
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Affiliation(s)
- Ketan D Patel
- University at Buffalo, Department of Structural Biology, Jacobs School of Medicine and Biomedical Sciences, 55 Main St. Buffalo, NY 14203, USA.
| | - Monica R MacDonald
- University at Buffalo, Department of Structural Biology, Jacobs School of Medicine and Biomedical Sciences, 55 Main St. Buffalo, NY 14203, USA.
| | - Syed Fardin Ahmed
- University at Buffalo, Department of Structural Biology, Jacobs School of Medicine and Biomedical Sciences, 55 Main St. Buffalo, NY 14203, USA.
| | - Jitendra Singh
- University at Buffalo, Department of Structural Biology, Jacobs School of Medicine and Biomedical Sciences, 55 Main St. Buffalo, NY 14203, USA.
| | - Andrew M Gulick
- University at Buffalo, Department of Structural Biology, Jacobs School of Medicine and Biomedical Sciences, 55 Main St. Buffalo, NY 14203, USA.
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4
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Kozyryev A, Boucher PA, Quiñones-Jurgensen CM, Rokita SE. The 2'-hydroxy group of flavin mononucleotide influences the catalytic function and promiscuity of the flavoprotein iodotyrosine dehalogenase. RSC Chem Biol 2023; 4:698-705. [PMID: 37654510 PMCID: PMC10467613 DOI: 10.1039/d3cb00094j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Accepted: 08/03/2023] [Indexed: 09/02/2023] Open
Abstract
The isoalloxazine ring system of the flavin cofactor is responsible for much of the catalytic power and diversity associated with flavoproteins. While the specificity of these enzymes is greatly influenced by the surrounding protein environment, the ribityl group of the cofactor may also participate in stabilizing transient intermediates formed by substrates and flavin. A conserved interaction between the phenolate oxygen of l-iodotyrosine and the 2'-hydroxy group of flavin mononucleotide (FMN) bound to iodotyrosine deiodianase (IYD) implied such a contribution to catalysis. Reconstitution of this deiodinase with 2'-deoxyflavin mononucleotide (2'-deoxyFMN) decreased the overall catalytic efficiency of l-iodotyrosine dehalogenation (kcat/Km) by more than 5-fold but increased kcat by over 2-fold. These affects are common to human IYD and its homolog from Thermotoga neapolitana and are best explained by an ability of the 2'-hydroxy group of FMN to stabilize association of the substrate in its phenolate form. Loss of this 2'-hydroxy group did not substantially affect the formation of the one electron reduced semiquinone form of FMN but its absence released constraints that otherwise suppresses the ability of IYD to promote hydride transfer as measured by a competing nitroreductase activity. Generation of IYD containing 2'-deoxyFMN also removed steric constraints that had previously limited the use of certain mechanistic probes. For example, l-O-methyl iodotyrosine could be accommodated in the active site lacking the 2'-hydroxy of FMN and shown to be inert to dehalogenation as predicted from a mechanism requiring ketonization of the phenolic oxygen. In the future, ancillary sites within a cofactor should now be considered when engineering new functions within existing protein architectures as demonstrated by the ability of IYD to promote nitroreduction after loss of the 2'-hydroxy group of FMN.
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Affiliation(s)
- Anton Kozyryev
- Department of Chemistry, Johns Hopkins University 3400 N. Charles St. Maryland 21218 USA +1-410-516-5793
| | - Petrina A Boucher
- Department of Chemistry, Johns Hopkins University 3400 N. Charles St. Maryland 21218 USA +1-410-516-5793
| | - Carla M Quiñones-Jurgensen
- Department of Chemistry, Johns Hopkins University 3400 N. Charles St. Maryland 21218 USA +1-410-516-5793
| | - Steven E Rokita
- Department of Chemistry, Johns Hopkins University 3400 N. Charles St. Maryland 21218 USA +1-410-516-5793
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5
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Kozyryev A, Lemen D, Dunn J, Rokita SE. Substrate Electronics Dominate the Rate of Reductive Dehalogenation Promoted by the Flavin-Dependent Iodotyrosine Deiodinase. Biochemistry 2023; 62:1298-1306. [PMID: 36892456 PMCID: PMC10073337 DOI: 10.1021/acs.biochem.3c00041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/10/2023]
Abstract
Iodotyrosine deiodinase (IYD) is unusual in its reliance on flavin to promote reductive dehalogenation of halotyrosines under aerobic conditions. Applications of this activity can be envisioned for bioremediation, but expansion of its specificity requires an understanding of the mechanistic steps that limit the rate of turnover. Key processes capable of controlling steady-state turnover have now been evaluated and described in this study. While proton transfer is necessary for converting the electron-rich substrate into an electrophilic intermediate suitable for reduction, kinetic solvent deuterium isotope effects suggest that this process does not contribute to the overall efficiency of catalysis under neutral conditions. Similarly, reconstituting IYD with flavin analogues demonstrates that a change in reduction potential by as much as 132 mV affects kcat by less than 3-fold. Furthermore, kcat/Km does not correlate with reduction potential and indicates that electron transfer is also not rate determining. Catalytic efficiency is most sensitive to the electronic nature of its substrates. Electron-donating substituents on the ortho position of iodotyrosine stimulate catalysis and conversely electron-withdrawing substituents suppress catalysis. Effects on kcat and kcat/Km range from 22- to 100-fold and fit a linear free-energy correlation with a ρ ranging from -2.1 to -2.8 for human and bacterial IYD. These values are consistent with a rate-determining process of stabilizing the electrophilic and nonaromatic intermediate poised for reduction. Future engineering can now focus on efforts to stabilize this electrophilic intermediate over a broad series of phenolic substrates that are targeted for removal from our environment.
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Affiliation(s)
- Anton Kozyryev
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, Maryland 21218 United States
| | - Daniel Lemen
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, Maryland 21218 United States
| | - Jessica Dunn
- Chemistry Biology Interface Graduate Program, Johns Hopkins University, 3400 N. Charles St., Baltimore, Maryland 21218 United States
| | - Steven E Rokita
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, Maryland 21218 United States
- Chemistry Biology Interface Graduate Program, Johns Hopkins University, 3400 N. Charles St., Baltimore, Maryland 21218 United States
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6
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Uppu RM, Fronczek FR. 1 H-Benzo[ g]pteridine-2,4-dione. IUCRDATA 2023; 8:x221223. [PMID: 36794048 PMCID: PMC9912317 DOI: 10.1107/s2414314622012238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Accepted: 12/29/2022] [Indexed: 01/09/2023] Open
Abstract
The structure of the title compound, C10H6N4O2, reported by Smalley et al. [(2021). Cryst. Growth Des. 22, 524-534] from powder diffraction data and 15N NMR spectroscopy, is confirmed using low-temperature data from a twinned crystal. The tautomer in the solid state is alloxazine (1H-benzo[g]pteridine-2,4-dione) rather than isoalloxazine (10H-benzo[g]pteridine-2,4-dione). In the extended structure, the mol-ecules form hydrogen-bonded chains propagating in the [01] direction through alternating centrosymmetric R 2 2(8) rings with pairwise N-H⋯O inter-actions and centrosymmetric R 2 2(8) rings with pairwise N-H⋯N inter-actions. The crystal chosen for data collection was found to be a non-merohedral twin (180° rotation about [001]) in a 0.446 (4):0.554 (6) domain ratio.
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Affiliation(s)
- Rao M. Uppu
- Department of Environmental Toxicology, Southern University and A&M College, Baton Rouge, LA 70813, USA,Correspondence e-mail:
| | - Frank R. Fronczek
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA
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Li Y, Mo H, Jia S, Wang J, Ma Y, Liu X, Tu K. Comprehensive analysis of the amino acid metabolism-related gene signature for prognosis, tumor immune microenvironment, and candidate drugs in hepatocellular carcinoma. Front Immunol 2022; 13:1066773. [PMID: 36582227 PMCID: PMC9792509 DOI: 10.3389/fimmu.2022.1066773] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 11/29/2022] [Indexed: 12/14/2022] Open
Abstract
Introduction Metabolic rewiring satisfies increased nutritional demands and modulates many oncogenic processes in tumors. Amino acid metabolism is abnormal in many malignancies. Metabolic reprogramming of amino acids not only plays a crucial role in sustaining tumor cell proliferation but also influences the tumor immune microenvironment. Herein, the aim of our study was to elucidate the metabolic signature of amino acids in hepatocellular carcinoma (HCC). Methods Transcriptome profiles of HCC were obtained from the TCGA and ICGC databases. Based on the expression of amino acid metabolism-related genes (AAMRGs), we clustered the HCC samples into two molecular subtypes using the non-negative matrix factorization algorithm. Then, we constructed the amino acid metabolism-related gene signature (AAMRGS) by Cox regression and LASSO regression. Afterward, the clinical significance of the AAMRGS was evaluated. Additionally, we comprehensively analyzed the differences in mutational profiles, immune cell infiltration, immune checkpoint expression, and drug sensitivity between different risk subgroups. Furthermore, we examined three key gene expressions in liver cancer cells by quantitative real-time PCR and conducted the CCK8 assay to evaluate the influence of two chemotherapy drugs on different liver cancer cells. Results A total of 81 differentially expressed AAMRGs were screened between the two molecular subtypes, and these AAMRGs were involved in regulating amino acid metabolism. The AAMRGS containing GLS, IYD, and NQO1 had a high value for prognosis prediction in HCC patients. Besides this, the two AAMRGS subgroups had different genetic mutation probabilities. More importantly, the immunosuppressive cells were more enriched in the AAMRGS-high group. The expression level of inhibitory immune checkpoints was also higher in patients with high AAMRGS scores. Additionally, the two AAMRGS subgroups showed different susceptibility to chemotherapeutic and targeted drugs. In vitro experiments showed that gemcitabine significantly reduced the proliferative capacity of SNU449 cells, and rapamycin remarkedly inhibited Huh7 proliferation. The five HCC cells displayed different mRNA expression levels of GLS, IYD, and NQO1. Conclusions Our study explored the features of amino acid metabolism in HCC and identified the novel AAMRGS to predict the prognosis, immune microenvironment, and drug sensitivity of HCC patients. These findings might help to guide personalized treatment and improve the clinical outcomes of HCC.
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Affiliation(s)
- Yue Li
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
| | - Huanye Mo
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
| | - Siying Jia
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
| | - Jun Wang
- Department of Emergency and Critical Care Medicine, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China
| | - Ying Ma
- Department of Cardiovascular Medicine, Xi’an No.3 Hospital, The Affiliated Hospital of Northwest University, Xi’an, China
| | - Xin Liu
- The Key Laboratory of Tumor Molecular Diagnosis and Individualized Medicine of Zhejiang Province, Zhejiang Provincial People’s Hospital, Affiliated People’s Hospital, Hangzhou Medical College, Hangzhou, China,*Correspondence: Xin Liu, ; Kangsheng Tu,
| | - Kangsheng Tu
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Xi’an Jiaotong University, Xi’an, China,*Correspondence: Xin Liu, ; Kangsheng Tu,
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8
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Musila JM, Rokita SE. Sequence Conservation Does Not Always Signify a Functional Imperative as Observed in the Nitroreductase Superfamily. Biochemistry 2022; 61:703-711. [PMID: 35319879 PMCID: PMC9018611 DOI: 10.1021/acs.biochem.2c00037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Consensus sequences have the potential to help classify the structure and function of proteins and highlight key regions that may contribute to their biological properties. Often, the level of significance will track with the extent of sequence conservation, but this should not be considered universal. Arg and Lys dominate a position adjacent to the N1 and C2 carbonyl of flavin mononucleotide (FMN) bound in the proteins of the nitroreductase superfamily. Although this placement satisfies expectations for stabilizing the reduced form of FMN, the substitution of these residues in three subfamilies promoting distinct reactions demonstrates their importance to catalysis as only modest. Replacing Arg34 with Lys, Gln, or Glu enhances FMN binding to a flavin destructase (BluB) by twofold and diminishes FMN turnover by no more than 25%. Similarly, replacing Lys14 with Arg, Gln, or Glu in a nitroreductase (NfsB) does not perturb the binding of the substrate nitrofurazone. The catalytic efficiency does decrease by 21-fold for the K14Q variant, but no change in the midpoint potential of FMN was observed with any of the variants. Equivalent substitution at Arg38 in iodotyrosine deiodinase (IYD) affects catalysis even more modestly (<10-fold). While the Arg/Lys to Glu substitution inactivates NfsB and IYD, this change also stabilizes one-electron transfer in IYD contrary to predictions based on other classes of flavoproteins. Accordingly, functional correlations developed in certain structural superfamilies may not necessarily translate well to other superfamilies.
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Affiliation(s)
- Jonathan M Musila
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Steven E Rokita
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
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9
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Lechner H, Oberdorfer G. Derivatives of natural organocatalytic cofactors and artificial organocatalytic cofactors as catalysts in enzymes. Chembiochem 2022; 23:e202100599. [PMID: 35302276 PMCID: PMC9401024 DOI: 10.1002/cbic.202100599] [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: 10/31/2021] [Revised: 03/14/2022] [Indexed: 11/11/2022]
Abstract
Catalytically active non-metal cofactors in enzymes carry out a variety of different reactions. The efforts to develop derivatives of natural occurring cofactors such as flavins or pyridoxal phosphate and the advances to design new, non-natural cofactors are reviewed here. We report the status quo for enzymes harboring organocatalysts as derivatives of natural cofactors or as artificial ones and their application in the asymmetric synthesis of various compounds.
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Affiliation(s)
- Horst Lechner
- Graz University of Technology: Technische Universitat Graz, Institute of Biochemistry, Petersgasse 12/2, 8010, Graz, AUSTRIA
| | - Gustav Oberdorfer
- Graz University of Technology: Technische Universitat Graz, Institute of Biochemistry, Petersgasse 12/2, 8010, Graz, AUSTRIA
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10
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Fortinez CM, Bloudoff K, Harrigan C, Sharon I, Strauss M, Schmeing TM. Structures and function of a tailoring oxidase in complex with a nonribosomal peptide synthetase module. Nat Commun 2022; 13:548. [PMID: 35087027 PMCID: PMC8795117 DOI: 10.1038/s41467-022-28221-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 12/19/2021] [Indexed: 12/15/2022] Open
Abstract
Nonribosomal peptide synthetases (NRPSs) are large modular enzymes that synthesize secondary metabolites and natural product therapeutics. Most NRPS biosynthetic pathways include an NRPS and additional proteins that introduce chemical modifications before, during or after assembly-line synthesis. The bacillamide biosynthetic pathway is a common, three-protein system, with a decarboxylase that prepares an NRPS substrate, an NRPS, and an oxidase. Here, the pathway is reconstituted in vitro. The oxidase is shown to perform dehydrogenation of the thiazoline in the peptide intermediate while it is covalently attached to the NRPS, as the penultimate step in bacillamide D synthesis. Structural analysis of the oxidase reveals a dimeric, two-lobed architecture with a remnant RiPP recognition element and a dramatic wrapping loop. The oxidase forms a stable complex with the NRPS and dimerizes it. We visualized co-complexes of the oxidase bound to the elongation module of the NRPS using X-ray crystallography and cryo-EM. The three active sites (for adenylation, condensation/cyclization, and oxidation) form an elegant arc to facilitate substrate delivery. The structures enabled a proof-of-principle bioengineering experiment in which the BmdC oxidase domain is embedded into the NRPS.
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Affiliation(s)
- Camille Marie Fortinez
- Department of Biochemistry, McGill University, Montréal, QC, H3G 0B1, Canada.,Centre de recherche en biologie structurale, McGill University, Montréal, QC, H3G 0B1, Canada
| | - Kristjan Bloudoff
- Department of Biochemistry, McGill University, Montréal, QC, H3G 0B1, Canada.,Centre de recherche en biologie structurale, McGill University, Montréal, QC, H3G 0B1, Canada
| | - Connor Harrigan
- Department of Biochemistry, McGill University, Montréal, QC, H3G 0B1, Canada.,Centre de recherche en biologie structurale, McGill University, Montréal, QC, H3G 0B1, Canada
| | - Itai Sharon
- Department of Biochemistry, McGill University, Montréal, QC, H3G 0B1, Canada.,Centre de recherche en biologie structurale, McGill University, Montréal, QC, H3G 0B1, Canada
| | - Mike Strauss
- Centre de recherche en biologie structurale, McGill University, Montréal, QC, H3G 0B1, Canada.,Department of Anatomy and Cell Biology, McGill University, Montréal, QC, H3A 0C7, Canada
| | - T Martin Schmeing
- Department of Biochemistry, McGill University, Montréal, QC, H3G 0B1, Canada. .,Centre de recherche en biologie structurale, McGill University, Montréal, QC, H3G 0B1, Canada.
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11
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Sun Z, Xu B, Spisak S, Kavran JM, Rokita SE. The minimal structure for iodotyrosine deiodinase function is defined by an outlier protein from the thermophilic bacterium Thermotoga neapolitana. J Biol Chem 2021; 297:101385. [PMID: 34748729 PMCID: PMC8668982 DOI: 10.1016/j.jbc.2021.101385] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 10/27/2021] [Accepted: 10/28/2021] [Indexed: 11/12/2022] Open
Abstract
The nitroreductase superfamily of enzymes encompasses many flavin mononucleotide (FMN)-dependent catalysts promoting a wide range of reactions. All share a common core consisting of an FMN-binding domain, and individual subgroups additionally contain one to three sequence extensions radiating from defined positions within this core to support their unique catalytic properties. To identify the minimum structure required for activity in the iodotyrosine deiodinase subgroup of this superfamily, attention was directed to a representative from the thermophilic organism Thermotoga neapolitana (TnIYD). This representative was selected based on its status as an outlier of the subgroup arising from its deficiency in certain standard motifs evident in all homologues from mesophiles. We found that TnIYD lacked a typical N-terminal sequence and one of its two characteristic sequence extensions, neither of which was found to be necessary for activity. We also show that TnIYD efficiently promotes dehalogenation of iodo-, bromo-, and chlorotyrosine, analogous to related deiodinases (IYDs) from humans and other mesophiles. In addition, 2-iodophenol is a weak substrate for TnIYD as it was for all other IYDs characterized to date. Consistent with enzymes from thermophilic organisms, we observed that TnIYD adopts a compact fold and low surface area compared with IYDs from mesophilic organisms. The insights gained from our investigations on TnIYD demonstrate the advantages of focusing on sequences that diverge from conventional standards to uncover the minimum essentials for activity. We conclude that TnIYD now represents a superior starting structure for future efforts to engineer a stable dehalogenase targeting halophenols of environmental concern.
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Affiliation(s)
- Zuodong Sun
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland, USA
| | - Bing Xu
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland, USA
| | - Shaun Spisak
- Chemistry-Biology Interface Graduate Program, Johns Hopkins University, Baltimore, Maryland, USA
| | - Jennifer M Kavran
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, USA; Department of Biophysics and Biophysical Chemistry, School of Medicine, Johns Hopkins University, Baltimore, Maryland, USA; Department of Oncology, School of Medicine, Johns Hopkins University, Baltimore, Maryland, USA
| | - Steven E Rokita
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland, USA.
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12
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Ospina F, Schülke KH, Hammer SC. Biocatalytic Alkylation Chemistry: Building Molecular Complexity with High Selectivity. Chempluschem 2021; 87:e202100454. [PMID: 34821073 DOI: 10.1002/cplu.202100454] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Revised: 11/05/2021] [Indexed: 12/28/2022]
Abstract
Biocatalysis has traditionally been viewed as a field that primarily enables access to chiral centers. This includes the synthesis of chiral alcohols, amines and carbonyl compounds, often through functional group interconversion via hydrolytic or oxidation-reduction reactions. This limitation is partly being overcome by the design and evolution of new enzymes. Here, we provide an overview of a recently thriving research field that we summarize as biocatalytic alkylation chemistry. In the past 3-4 years, numerous new enzymes have been developed that catalyze sp3 C-C/N/O/S bond formations. These enzymes utilize different mechanisms to generate molecular complexity by coupling simple fragments with high activity and selectivity. In many cases, the engineered enzymes perform reactions that are difficult or impossible to achieve with current small-molecule catalysts such as organocatalysts and transition-metal complexes. This review further highlights that the design of new enzyme function is particularly successful when off-the-shelf synthetic reagents are utilized to access non-natural reactive intermediates. This underscores how biocatalysis is gradually moving to a field that build molecules through selective bond forming reactions.
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Affiliation(s)
- Felipe Ospina
- Faculty of Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Kai H Schülke
- Faculty of Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Stephan C Hammer
- Faculty of Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
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Coscia F, Taler-Verčič A. Cryo-EM: A new dawn in thyroid biology. Mol Cell Endocrinol 2021; 531:111309. [PMID: 33964321 PMCID: PMC8316605 DOI: 10.1016/j.mce.2021.111309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Revised: 04/25/2021] [Accepted: 04/27/2021] [Indexed: 11/09/2022]
Abstract
The thyroid gland accumulates the rare dietary element iodine and incorporates it into iodinated thyroid hormones, utilising several tightly regulated reactions and molecular mechanisms. Thyroid hormones are essential in vertebrates and play a central role in many biological processes, such as development, thermogenesis and growth. The control of these functions is exerted through the binding of hormones to nuclear thyroid hormone receptors that rule the transcription of numerous metabolic genes. Over the last 50 years, thyroid biology has been studied extensively at the cellular and organismal levels, revealing its multiple clinical implications, yet, a complete molecular understanding is still lacking. This includes the atomic structures of crucial pathway components that would be needed to elucidate molecular mechanisms. Here we review the currently known protein structures involved in thyroid hormone synthesis, regulation, transport, and actions. We also highlight targets for future investigations that will significantly benefit from recent advances in macromolecular structure determination by electron cryo-microscopy (cryo-EM). As an example, we demonstrate how cryo-EM was crucial to obtain the structure of the large thyroid hormone precursor protein, thyroglobulin. We discuss modern cryo-EM compared to other structure determination methods and how an integrated structural and cell biological approach will help filling the molecular knowledge gap in our understanding of thyroid hormone metabolism. Together with clinical, cellular and high-throughput 'omics' studies, atomic structures of thyroid components will provide an important framework to map disease mutations and to interpret and predict thyroid phenotypes.
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Affiliation(s)
- Francesca Coscia
- MRC Laboratory of Molecular Biology, Cambridge, CB2 0QH, UK; Human Technopole, Via Cristina Belgioioso 171, 20157, Milano, Italy.
| | - Ajda Taler-Verčič
- University of Ljubljana, Faculty of Medicine, Institute of Biochemistry and Molecular Genetics, Vrazov Trg 2, 1000, Ljubljana, Slovenia
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14
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Sobrado P. Role of reduced flavin in dehalogenation reactions. Arch Biochem Biophys 2020; 697:108696. [PMID: 33245912 DOI: 10.1016/j.abb.2020.108696] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Revised: 11/12/2020] [Accepted: 11/18/2020] [Indexed: 12/14/2022]
Abstract
Halogenated organic compounds are extensively used in the cosmetic, pharmaceutical, and chemical industries. Several naturally occurring halogen-containing natural products are also produced, mainly by marine organisms. These compounds accumulate in the environment due to their chemical stability and lack of biological pathways for their degradation. However, a few enzymes have been identified that perform dehalogenation reactions in specific biological pathways and others have been identified to have secondary activities toward halogenated compounds. Various mechanisms for dehalogenation of I, Cl, Br, and F containing compounds have been elucidated. These have been grouped into reductive, oxidative, and hydrolytic mechanisms. Flavin-dependent enzymes have been shown to catalyze oxidative dehalogenation reactions utilizing the C4a-hydroperoxyflavin intermediate. In addition, flavoenzymes perform reductive dehalogenation, forming transient flavin semiquinones. Recently, flavin-dependent enzymes have also been shown to perform dehalogenation reactions where the reduced form of the flavin produces a covalent intermediate. Here, recent studies on the reactions of flavoenzymes in dehalogenation reactions, with a focus on covalent catalytic dehalogenation mechanisms, are described.
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Affiliation(s)
- Pablo Sobrado
- Department of Biochemistry and Center for Drug Discovery, Virginia Tech, Blacksburg, VA, 24061, USA.
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15
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Dabravolski SA. Evolutionary aspects of the Viridiplantae nitroreductases. J Genet Eng Biotechnol 2020; 18:60. [PMID: 33025290 PMCID: PMC7538488 DOI: 10.1186/s43141-020-00073-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 09/14/2020] [Indexed: 11/10/2022]
Abstract
Background Nitroreductases are a family of evolutionarily related proteins catalyzing the reduction of nitro-substituted compounds. Nitroreductases are widespread enzymes, but nearly all modern research and practical application have been concentrated on the bacterial proteins, mainly nitroreductases of Escherichia coli. The main aim of this study is to describe the phylogenic distribution of the nitroreductases in the photosynthetic eukaryotes (Viridiplantae) to highlight their structural similarity and areas for future research and application. Results This study suggests that homologs of nitroreductase proteins are widely presented also in Viridiplantae. Maximum likelihood phylogenetic tree reconstruction method and comparison of the structural models suggest close evolutional relation between cyanobacterial and Viridiplantae nitroreductases. Conclusions This study provides the first attempt to understand the evolution of nitroreductase protein family in Viridiplantae. Our phylogeny estimation and preservation of the chloroplasts/mitochondrial localization indicate the evolutional origin of the plant nitroreductases from the cyanobacterial endosymbiont. A defined high level of the similarity on the structural level suggests conservancy also for the functions. Directions for the future research and industrial application of the Viridiplantae nitroreductases are discussed.
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Affiliation(s)
- Siarhei A Dabravolski
- Department of Clinical Diagnostics, Vitebsk State Academy of Veterinary Medicine [UO VGAVM], 7/11 Dovatora St., 210026, Vitebsk, Belarus.
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16
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Duan HD, Mohamed-Raseek N, Miller AF. Spectroscopic evidence for direct flavin-flavin contact in a bifurcating electron transfer flavoprotein. J Biol Chem 2020; 295:12618-12634. [PMID: 32661195 DOI: 10.1074/jbc.ra120.013174] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 07/10/2020] [Indexed: 12/15/2022] Open
Abstract
A remarkable charge transfer (CT) band is described in the bifurcating electron transfer flavoprotein (Bf-ETF) from Rhodopseudomonas palustris (RpaETF). RpaETF contains two FADs that play contrasting roles in electron bifurcation. The Bf-FAD accepts electrons pairwise from NADH, directs one to a lower-reduction midpoint potential (E°) carrier, and the other to the higher-E° electron transfer FAD (ET-FAD). Previous work noted that a CT band at 726 nm formed when ET-FAD was reduced and Bf-FAD was oxidized, suggesting that both flavins participate. However, existing crystal structures place them too far apart to interact directly. We present biochemical experiments addressing this conundrum and elucidating the nature of this CT species. We observed that RpaETF missing either FAD lacked the 726 nm band. Site-directed mutagenesis near either FAD produced altered yields of the CT species, supporting involvement of both flavins. The residue substitutions did not alter the absorption maximum of the signal, ruling out contributions from residue orbitals. Instead, we propose that the residue identities modulate the population of a protein conformation that brings the ET-flavin and Bf-flavin into direct contact, explaining the 726 nm band based on a CT complex of reduced ET-FAD and oxidized Bf-FAD. This is corroborated by persistence of the 726 nm species during gentle protein denaturation and simple density functional theory calculations of flavin dimers. Although such a CT complex has been demonstrated for free flavins, this is the first observation of such, to our knowledge, in an enzyme. Thus, Bf-ETFs may optimize electron transfer efficiency by enabling direct flavin-flavin contact.
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Affiliation(s)
- H Diessel Duan
- Department of Chemistry, University of Kentucky, Lexington, Kentucky, USA
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17
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Sandoval BA, Hyster TK. Emerging strategies for expanding the toolbox of enzymes in biocatalysis. Curr Opin Chem Biol 2020; 55:45-51. [PMID: 31935627 PMCID: PMC7769163 DOI: 10.1016/j.cbpa.2019.12.006] [Citation(s) in RCA: 62] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 12/12/2019] [Accepted: 12/13/2019] [Indexed: 11/30/2022]
Abstract
Expanding the repertoire of reactions available to enzymes is an enduring challenge in biocatalysis. Owing to the synthetic versatility of transition metals, metalloenzymes have been favored targets for achieving new catalytic functions. Although less well explored, enzymes lacking metal centers can also be effective catalysts for non-natural reactions, providing access to reaction modalities that compliment those available to metals. By understanding how these activation modes can reveal new functions, strategies can be developed to access novel biocatalytic reactions. This review will cover discoveries in the last two years which access catalytic reactions that go beyond the native repertoire of metal-free biocatalysts.
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Affiliation(s)
| | - Todd K Hyster
- Department of Chemistry, Princeton University, Princeton, NJ, 08544, USA.
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18
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19
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Miller AF, Duan HD, Varner TA, Mohamed Raseek N. Reduction midpoint potentials of bifurcating electron transfer flavoproteins. Methods Enzymol 2019; 620:365-398. [PMID: 31072494 DOI: 10.1016/bs.mie.2019.03.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Recently, a variety of enzymes have been found to accept electrons from NAD(P)H yet reduce lower-potential carriers such as ferredoxin and flavodoxin semiquinone, in apparent violation of thermodynamics. The reaction is favorable overall, however, because these enzymes couple the foregoing endergonic one-electron transfer to exergonic transfer of the other electron from each NAD(P)H, in a process called "flavin-based electron bifurcation." The reduction midpoint potentials (E°s) of the multiple flavins in these enzymes are critical to their mechanisms. We describe methods we have found to be useful for measuring each of the E°s of each of the flavins in bifurcating electron transfer flavoproteins.
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Affiliation(s)
- A-F Miller
- Department of Chemistry, University of Kentucky, Lexington, KY, United States.
| | - H D Duan
- Department of Chemistry, University of Kentucky, Lexington, KY, United States
| | - T A Varner
- Department of Chemistry, University of Kentucky, Lexington, KY, United States
| | - N Mohamed Raseek
- Department of Chemistry, University of Kentucky, Lexington, KY, United States
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20
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Hu J, Su Q, Schlessman JL, Rokita SE. Redox control of iodotyrosine deiodinase. Protein Sci 2019; 28:68-78. [PMID: 30052294 PMCID: PMC6296174 DOI: 10.1002/pro.3479] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Revised: 07/03/2018] [Accepted: 07/05/2018] [Indexed: 12/29/2022]
Abstract
The redox chemistry of flavoproteins is often gated by substrate and iodotyrosine deiodinase (IYD) has the additional ability to switch between reaction modes based on the substrate. Association of fluorotyrosine (F-Tyr), an inert substrate analog, stabilizes single electron transfer reactions of IYD that are not observed in the absence of this ligand. The co-crystal of F-Tyr and a T239A variant of human IYD have now been characterized to provide a structural basis for control of its flavin reactivity. Coordination of F-Tyr in the active site of this IYD closely mimics that of iodotyrosine and only minor perturbations are observed after replacement of an active site Thr with Ala. However, loss of the side chain hydroxyl group removes a key hydrogen bond from flavin and suppresses the formation of its semiquinone intermediate. Even substitution of Thr with Ser decreases the midpoint potential of human IYD between its oxidized and semiquinone forms of flavin by almost 80 mV. This decrease does not adversely affect the kinetics of reductive dehalogenation although an analogous Ala variant exhibits a 6.7-fold decrease in its kcat /Km . Active site ligands lacking the zwitterion of halotyrosine are not able to induce closure of the active site lid that is necessary for promoting single electron transfer and dehalogenation. Under these conditions, a basal two-electron process dominates catalysis as indicated by preferential reduction of nitrophenol rather than deiodination of iodophenol.
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Affiliation(s)
- Jimin Hu
- Department of ChemistryJohns Hopkins UniversityBaltimoreMaryland, 21218
| | - Qi Su
- Department of ChemistryJohns Hopkins UniversityBaltimoreMaryland, 21218
| | | | - Steven E. Rokita
- Department of ChemistryJohns Hopkins UniversityBaltimoreMaryland, 21218
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21
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Adak S, Begley TP. Flavin-N5-oxide intermediates in dibenzothiophene, uracil, and hexachlorobenzene catabolism. Methods Enzymol 2019; 620:455-468. [DOI: 10.1016/bs.mie.2019.03.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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22
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23
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Sun Z, Rokita SE. Toward a Halophenol Dehalogenase from Iodotyrosine Deiodinase via Computational Design. ACS Catal 2018. [DOI: 10.1021/acscatal.8b03587] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Zuodong Sun
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, Maryland 21218, United States
| | - Steven E. Rokita
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, Maryland 21218, United States
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24
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Biocatalytic hydrogen atom transfer: an invigorating approach to free-radical reactions. Curr Opin Chem Biol 2018; 49:16-24. [PMID: 30269010 DOI: 10.1016/j.cbpa.2018.09.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Accepted: 09/02/2018] [Indexed: 10/28/2022]
Abstract
Initiating and terminating free-radical reactionis via hydrogen atom transfer (HAT) is an attractive means of avoiding substrate prefunctionalization. Small molecule catalysts and reagents, however, struggle to execute this fundamental step with useful levels of diastereoselectivity and enantioselectivity. In contrast, nature often carries out HAT with exquisite levels of selectivity for even electronically unactivated carbon-hydrogen bonds. By understanding how enzymes exploit and control this fundamental step, new strategies can be developed to address several long-standing challenges in free-radical reactions. This review will cover recent discoveries in biocatalysis that exploit a HAT mechanism to either initiate or terminate novel one-electron reactions.
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25
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Phatarphekar A, Su Q, Eun SH, Chen X, Rokita SE. The importance of a halotyrosine dehalogenase for Drosophila fertility. J Biol Chem 2018; 293:10314-10321. [PMID: 29764939 DOI: 10.1074/jbc.ra118.003364] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2018] [Revised: 05/11/2018] [Indexed: 12/18/2022] Open
Abstract
The ability of iodotyrosine deiodinase to salvage iodide from iodotyrosine has long been recognized as critical for iodide homeostasis and proper thyroid function in vertebrates. The significance of its additional ability to dehalogenate bromo- and chlorotyrosine is less apparent, and none of these functions could have been anticipated in invertebrates until recently. Drosophila, as most arthropods, contains a deiodinase homolog encoded by CG6279, now named condet (cdt), with a similar catalytic specificity. However, its physiological role cannot be equivalent because Drosophila lacks a thyroid and its associated hormones, and no requirement for iodide or halotyrosines has been reported for this species. We have now applied CRISPR/Cas9 technology to generate Drosophila strains in which the cdt gene has been either deleted or mutated to identify its biological function. As previously shown in larvae, expression of cdt is primarily limited to the fat body, and we now report that loss of cdt function does not enhance sensitivity of the larvae to the toxic effects of iodotyrosine. In adult flies by contrast, expression is known to occur in testes and is detected at very high levels in this tissue. The importance of cdt is most evident in the decrease in fertility observed when either males or females carry a deletion or mutation of cdt Therefore, dehalogenation of a halotyrosine appears essential for efficient reproduction in Drosophila and likely contributes to a new pathway for controlling viability in arthropods.
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Affiliation(s)
| | - Qi Su
- From the Departments of Chemistry and
| | - Suk Ho Eun
- Biology, Johns Hopkins University, Baltimore, Maryland 21218
| | - Xin Chen
- Biology, Johns Hopkins University, Baltimore, Maryland 21218
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26
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Sellés Vidal L, Kelly CL, Mordaka PM, Heap JT. Review of NAD(P)H-dependent oxidoreductases: Properties, engineering and application. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2017; 1866:327-347. [PMID: 29129662 DOI: 10.1016/j.bbapap.2017.11.005] [Citation(s) in RCA: 164] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 10/27/2017] [Accepted: 11/08/2017] [Indexed: 11/27/2022]
Abstract
NAD(P)H-dependent oxidoreductases catalyze the reduction or oxidation of a substrate coupled to the oxidation or reduction, respectively, of a nicotinamide adenine dinucleotide cofactor NAD(P)H or NAD(P)+. NAD(P)H-dependent oxidoreductases catalyze a large variety of reactions and play a pivotal role in many central metabolic pathways. Due to the high activity, regiospecificity and stereospecificity with which they catalyze redox reactions, they have been used as key components in a wide range of applications, including substrate utilization, the synthesis of chemicals, biodegradation and detoxification. There is great interest in tailoring NAD(P)H-dependent oxidoreductases to make them more suitable for particular applications. Here, we review the main properties and classes of NAD(P)H-dependent oxidoreductases, the types of reactions they catalyze, some of the main protein engineering techniques used to modify their properties and some interesting examples of their modification and application.
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Affiliation(s)
- Lara Sellés Vidal
- Centre for Synthetic Biology and Innovation, Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Ciarán L Kelly
- Centre for Synthetic Biology and Innovation, Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Paweł M Mordaka
- Centre for Synthetic Biology and Innovation, Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - John T Heap
- Centre for Synthetic Biology and Innovation, Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom.
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27
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Su Q, Boucher PA, Rokita SE. Conversion of a Dehalogenase into a Nitroreductase by Swapping its Flavin Cofactor with a 5-Deazaflavin Analogue. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201703628] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Qi Su
- Department of Chemistry; Johns Hopkins University; 3400 N. Charles St. Baltimore MD 21218 USA
| | - Petrina A. Boucher
- Department of Chemistry; Johns Hopkins University; 3400 N. Charles St. Baltimore MD 21218 USA
| | - Steven E. Rokita
- Department of Chemistry; Johns Hopkins University; 3400 N. Charles St. Baltimore MD 21218 USA
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28
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Sandoval BA, Meichan AJ, Hyster TK. Enantioselective Hydrogen Atom Transfer: Discovery of Catalytic Promiscuity in Flavin-Dependent 'Ene'-Reductases. J Am Chem Soc 2017; 139:11313-11316. [PMID: 28780870 DOI: 10.1021/jacs.7b05468] [Citation(s) in RCA: 90] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Flavin has long been known to function as a single electron reductant in biological settings, but this reactivity has rarely been observed with flavoproteins used in organic synthesis. Here we describe the discovery of an enantioselective radical dehalogenation pathway for α-bromoesters using flavin-dependent 'ene'-reductases. Mechanistic experiments support the role of flavin hydroquinone as a single electron reductant, flavin semiquinone as the hydrogen atom source, and the enzyme as the source of chirality.
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Affiliation(s)
- Braddock A Sandoval
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
| | - Andrew J Meichan
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
| | - Todd K Hyster
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
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29
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Sun Z, Su Q, Rokita SE. The distribution and mechanism of iodotyrosine deiodinase defied expectations. Arch Biochem Biophys 2017; 632:77-87. [PMID: 28774660 DOI: 10.1016/j.abb.2017.07.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 07/24/2017] [Accepted: 07/30/2017] [Indexed: 12/19/2022]
Abstract
Iodotyrosine deiodinase (IYD) is unusual for its reliance on flavin to promote reductive dehalogenation under aerobic conditions. As implied by the name, this enzyme was first discovered to catalyze iodide elimination from iodotyrosine for recycling iodide during synthesis of tetra- and triiodothyronine collectively known as thyroid hormone. However, IYD likely supports many more functions and has been shown to debrominate and dechlorinate bromo- and chlorotyrosines. A specificity for halotyrosines versus halophenols is well preserved from humans to bacteria. In all examples to date, the substrate zwitterion establishes polar contacts with both the protein and the isoalloxazine ring of flavin. Mechanistic data suggest dehalogenation is catalyzed by sequential one electron transfer steps from reduced flavin to substrate despite the initial expectations for a single two electron transfer mechanism. A purported flavin semiquinone intermediate is stabilized by hydrogen bonding between its N5 position and the side chain of a Thr. Mutation of this residue to Ala suppresses dehalogenation and enhances a nitroreductase activity that is reminiscent of other enzymes within the same structural superfamily.
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Affiliation(s)
- Zuodong Sun
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA
| | - Qi Su
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA
| | - Steven E Rokita
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218, USA.
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30
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Su Q, Boucher PA, Rokita SE. Conversion of a Dehalogenase into a Nitroreductase by Swapping its Flavin Cofactor with a 5-Deazaflavin Analogue. Angew Chem Int Ed Engl 2017; 56:10862-10866. [PMID: 28666054 DOI: 10.1002/anie.201703628] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Revised: 06/14/2017] [Indexed: 11/05/2022]
Abstract
Natural and engineered nitroreductases have rarely supported full reduction of nitroaromatics to their amine products, and more typically, transformations are limited to formation of the hydroxylamine intermediates. Efficient use of these enzymes also requires a regenerating system for NAD(P)H to avoid the costs associated with this natural reductant. Iodotyrosine deiodinase is a member of the same structural superfamily as many nitroreductases but does not directly consume reducing equivalents from NAD(P)H, nor demonstrate nitroreductase activity. However, exchange of its flavin cofactor with a 5-deazaflavin analogue dramatically suppresses its native deiodinase activity and leads to significant nitroreductase activity that supports full reduction to an amine product in the presence of the convenient and inexpensive NaBH4 .
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Affiliation(s)
- Qi Su
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD, 21218, USA
| | - Petrina A Boucher
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD, 21218, USA
| | - Steven E Rokita
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD, 21218, USA
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31
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Agarwal V, Miles ZD, Winter JM, Eustáquio AS, El Gamal AA, Moore BS. Enzymatic Halogenation and Dehalogenation Reactions: Pervasive and Mechanistically Diverse. Chem Rev 2017; 117:5619-5674. [PMID: 28106994 PMCID: PMC5575885 DOI: 10.1021/acs.chemrev.6b00571] [Citation(s) in RCA: 248] [Impact Index Per Article: 35.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Naturally produced halogenated compounds are ubiquitous across all domains of life where they perform a multitude of biological functions and adopt a diversity of chemical structures. Accordingly, a diverse collection of enzyme catalysts to install and remove halogens from organic scaffolds has evolved in nature. Accounting for the different chemical properties of the four halogen atoms (fluorine, chlorine, bromine, and iodine) and the diversity and chemical reactivity of their organic substrates, enzymes performing biosynthetic and degradative halogenation chemistry utilize numerous mechanistic strategies involving oxidation, reduction, and substitution. Biosynthetic halogenation reactions range from simple aromatic substitutions to stereoselective C-H functionalizations on remote carbon centers and can initiate the formation of simple to complex ring structures. Dehalogenating enzymes, on the other hand, are best known for removing halogen atoms from man-made organohalogens, yet also function naturally, albeit rarely, in metabolic pathways. This review details the scope and mechanism of nature's halogenation and dehalogenation enzymatic strategies, highlights gaps in our understanding, and posits where new advances in the field might arise in the near future.
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Affiliation(s)
- Vinayak Agarwal
- Center for Oceans and Human Health, Scripps Institution of Oceanography, University of California, San Diego
| | - Zachary D. Miles
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego
| | | | - Alessandra S. Eustáquio
- College of Pharmacy, Department of Medicinal Chemistry & Pharmacognosy and Center for Biomolecular Sciences, University of Illinois at Chicago
| | - Abrahim A. El Gamal
- Center for Oceans and Human Health, Scripps Institution of Oceanography, University of California, San Diego
| | - Bradley S. Moore
- Center for Oceans and Human Health, Scripps Institution of Oceanography, University of California, San Diego
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California, San Diego
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego
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32
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Ingavat N, Kavran JM, Sun Z, Rokita SE. Active Site Binding Is Not Sufficient for Reductive Deiodination by Iodotyrosine Deiodinase. Biochemistry 2017; 56:1130-1139. [PMID: 28157283 PMCID: PMC5330855 DOI: 10.1021/acs.biochem.6b01308] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The minimal requirements for substrate recognition and turnover by iodotyrosine deiodinase were examined to learn the basis for its catalytic specificity. This enzyme is crucial for iodide homeostasis and the generation of thyroid hormone in chordates. 2-Iodophenol binds only very weakly to the human enzyme and is dehalogenated with a kcat/Km that is more than 4 orders of magnitude lower than that for iodotyrosine. This discrimination likely protects against a futile cycle of iodinating and deiodinating precursors of thyroid hormone biosynthesis. Surprisingly, a very similar catalytic selectivity was expressed by a bacterial homologue from Haliscomenobacter hydrossis. In this example, discrimination was not based on affinity since 4-cyano-2-iodophenol bound to the bacterial deiodinase with a Kd lower than that of iodotyrosine and yet was not detectably deiodinated. Other phenols including 2-iodophenol were deiodinated but only very inefficiently. Crystal structures of the bacterial enzyme with and without bound iodotyrosine are nearly superimposable and quite similar to the corresponding structures of the human enzyme. Likewise, the bacterial enzyme is activated for single electron transfer after binding to the substrate analogue fluorotyrosine as previously observed with the human enzyme. A cocrystal structure of bacterial deiodinase and 2-iodophenol indicates that this ligand stacks on the active site flavin mononucleotide (FMN) in a orientation analogous to that of bound iodotyrosine. However, 2-iodophenol association is not sufficient to activate the FMN chemistry required for catalysis, and thus the bacterial enzyme appears to share a similar specificity for halotyrosines even though their physiological roles are likely very different from those in humans.
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Affiliation(s)
- Nattha Ingavat
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218 United States
| | - Jennifer M. Kavran
- Department of Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street Baltimore, Maryland 21205 United States,Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, 925 North Wolfe Street Baltimore, Maryland, 21205 United States
| | - Zuodong Sun
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218 United States
| | - Steven E. Rokita
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218 United States,Corresponding Author:
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Pimviriyakul P, Thotsaporn K, Sucharitakul J, Chaiyen P. Kinetic Mechanism of the Dechlorinating Flavin-dependent Monooxygenase HadA. J Biol Chem 2017; 292:4818-4832. [PMID: 28159841 DOI: 10.1074/jbc.m116.774448] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Revised: 01/30/2017] [Indexed: 01/26/2023] Open
Abstract
The accumulation of chlorophenols (CPs) in the environment, due to their wide use as agrochemicals, has become a serious environmental problem. These organic halides can be degraded by aerobic microorganisms, where the initial steps of various biodegradation pathways include an oxidative dechlorinating process in which chloride is replaced by a hydroxyl substituent. Harnessing these dechlorinating processes could provide an opportunity for environmental remediation, but detailed catalytic mechanisms for these enzymes are not yet known. To close this gap, we now report transient kinetics and product analysis of the dechlorinating flavin-dependent monooxygenase, HadA, from the aerobic organism Ralstonia pickettii DTP0602, identifying several mechanistic properties that differ from other enzymes in the same class. We first overexpressed and purified HadA to homogeneity. Analyses of the products from single and multiple turnover reactions demonstrated that HadA prefers 4-CP and 2-CP over CPs with multiple substituents. Stopped-flow and rapid-quench flow experiments of HadA with 4-CP show the involvement of specific intermediates (C4a-hydroperoxy-FAD and C4a-hydroxy-FAD) in the reaction, define rate constants and the order of substrate binding, and demonstrate that the hydroxylation step occurs prior to chloride elimination. The data also identify the non-productive and productive paths of the HadA reactions and demonstrate that product formation is the rate-limiting step. This is the first elucidation of the kinetic mechanism of a two-component flavin-dependent monooxygenase that can catalyze oxidative dechlorination of various CPs, and as such it will serve as the basis for future investigation of enzyme variants that will be useful for applications in detoxifying chemicals hazardous to human health.
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Affiliation(s)
- Panu Pimviriyakul
- From the Department of Biochemistry and Center for Excellence in Protein and Enzyme Technology, Faculty of Science, Mahidol University, Bangkok 10400 and
| | - Kittisak Thotsaporn
- the Department of Biochemistry, Faculty of Dentistry, Chulalongkorn University, Bangkok 10300, Thailand
| | - Jeerus Sucharitakul
- the Department of Biochemistry, Faculty of Dentistry, Chulalongkorn University, Bangkok 10300, Thailand
| | - Pimchai Chaiyen
- From the Department of Biochemistry and Center for Excellence in Protein and Enzyme Technology, Faculty of Science, Mahidol University, Bangkok 10400 and
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Leys D, Scrutton NS. Sweating the assets of flavin cofactors: new insight of chemical versatility from knowledge of structure and mechanism. Curr Opin Struct Biol 2016; 41:19-26. [DOI: 10.1016/j.sbi.2016.05.014] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Accepted: 05/24/2016] [Indexed: 10/21/2022]
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Phatarphekar A, Rokita SE. Functional analysis of iodotyrosine deiodinase from drosophila melanogaster. Protein Sci 2016; 25:2187-2195. [PMID: 27643701 DOI: 10.1002/pro.3044] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 09/13/2016] [Accepted: 09/14/2016] [Indexed: 01/28/2023]
Abstract
The flavoprotein iodotyrosine deiodinase (IYD) was first discovered in mammals through its ability to salvage iodide from mono- and diiodotyrosine, the by-products of thyroid hormone synthesis. Genomic information indicates that invertebrates contain homologous enzymes although their iodide requirements are unknown. The catalytic domain of IYD from Drosophila melanogaster has now been cloned, expressed and characterized to determine the scope of its potential catalytic function as a model for organisms that are not associated with thyroid hormone production. Little discrimination between iodo-, bromo-, and chlorotyrosine was detected. Their affinity for IYD ranges from 0.46 to 0.62 μM (Kd ) and their efficiency of dehalogenation ranges from 2.4 - 9 x 103 M-1 s-1 (kcat /Km ). These values fall within the variations described for IYDs from other organisms for which a physiological function has been confirmed. The relative contribution of three active site residues that coordinate to the amino acid substrates was subsequently determined by mutagenesis of IYD from Drosophila to refine future annotations of genomic and meta-genomic data for dehalogenation of halotyrosines. Substitution of the active site glutamate to glutamine was most detrimental to catalysis. Alternative substitution of an active site lysine to glutamine affected substrate affinity to the greatest extent but only moderately affected catalytic turnover. Substitution of phenylalanine for an active site tyrosine was least perturbing for binding and catalysis.
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Affiliation(s)
- Abhishek Phatarphekar
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St, Baltimore, Maryland, 21218
| | - Steven E Rokita
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles St, Baltimore, Maryland, 21218
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Mukherjee A, Rokita SE. Single Amino Acid Switch between a Flavin-Dependent Dehalogenase and Nitroreductase. J Am Chem Soc 2015; 137:15342-5. [PMID: 26616824 PMCID: PMC4684082 DOI: 10.1021/jacs.5b07540] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
A single
mutation within a flavoprotein is capable of switching
the catalytic activity of a dehalogenase into a nitroreductase.
This change in function correlates with a destabilization of the one-electron-reduced
flavin semiquinone that is differentially expressed in the nitro-FMN
reductase superfamily during redox cycling. The diversity of
function within such a superfamily therefore has the potential
to arise from rapid evolution, and its members should provide a convenient
basis for developing new catalysts with an altered specificity of
choice.
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Affiliation(s)
- Arnab Mukherjee
- Department of Chemistry, Johns Hopkins University , Baltimore, Maryland 21218, United States
| | - Steven E Rokita
- Department of Chemistry, Johns Hopkins University , Baltimore, Maryland 21218, United States
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Schweizer U, Steegborn C. New insights into the structure and mechanism of iodothyronine deiodinases. J Mol Endocrinol 2015; 55:R37-52. [PMID: 26390881 DOI: 10.1530/jme-15-0156] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/16/2015] [Indexed: 12/30/2022]
Abstract
Iodothyronine deiodinases are a family of enzymes that remove specific iodine atoms from one of the two aromatic rings in thyroid hormones (THs). They thereby fine-tune local TH concentrations and cellular TH signaling. Deiodinases catalyze a remarkable biochemical reaction, i.e., the reductive elimination of a halogenide from an aromatic ring. In metazoans, deiodinases depend on the rare amino acid selenocysteine. The recent solution of the first experimental structure of a deiodinase catalytic domain allowed for a reappraisal of the many mechanistic and mutagenesis data that had been accumulated over more than 30 years. Hence, the structure generates new impetus for research directed at understanding catalytic mechanism, substrate specificity, and regulation of deiodinases. This review will focus on structural and mechanistic aspects of iodothyronine deiodinases and briefly compare these enzymes with dehalogenases, which catalyze related reactions. A general mechanism for the selenium-dependent deiodinase reaction will be described, which integrates the mouse deiodinase 3 crystal structure and biochemical studies. We will summarize further, sometimes isoform-specific molecular features of deiodinase catalysis and regulation, and we will then discuss available compounds for modulating deiodinase activity for therapeutic purposes.
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Affiliation(s)
| | - Clemens Steegborn
- Institut für Biochemie und MolekularbiologieRheinische Friedrich-Wilhelms-Universität Bonn, Nussallee 11, 53115 Bonn, GermanyLehrstuhl BiochemieUniversität Bayreuth, Universitätsstrasse 30, 95445 Bayreuth, Germany
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Bobyk KD, Ballou DP, Rokita SE. Rapid kinetics of dehalogenation promoted by iodotyrosine deiodinase from human thyroid. Biochemistry 2015; 54:4487-94. [PMID: 26151430 PMCID: PMC4938124 DOI: 10.1021/acs.biochem.5b00410] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
![]()
Reductive dehalogenation such as
that catalyzed by iodotyrosine
deiodinase (IYD) is highly unusual in aerobic organisms but necessary
for iodide salvage from iodotyrosine generated during thyroxine biosynthesis.
Equally unusual is the dependence of this process on flavin. Rapid
kinetics have now been used to define the basic processes involved
in IYD catalysis. Time-dependent quenching of flavin fluorescence
was used to monitor halotyrosine association to IYD. The substrates
chloro-, bromo-, and iodotyrosine bound with similar rate constants
(kon) ranging from 1.3 × 106 to 1.9 × 106 M–1 s–1. Only the inert substrate analogue fluorotyrosine exhibited a significantly
(5-fold) slower kon (0.3 × 106 M–1 s–1). All data fit
a standard two-state model and indicated that no intermediate complex
accumulated during closure of the active site lid induced by substrate.
Subsequent halide elimination does not appear to limit reactions of
bromo- and iodotyrosine since both fully oxidized the reduced enzyme
with nearly equivalent second-order rate constants (7.3 × 103 and 8.6 × 103 M–1 s–1, respectively) despite the differing strength of
their carbon–halogen bonds. In contrast to these substrates,
chlorotyrosine reacted with the reduced enzyme approximately 20-fold
more slowly and revealed a spectral intermediate that formed at approximately
the same rate as the bromo- and iodotyrosine reactions.
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Affiliation(s)
- Kostyantyn D Bobyk
- †Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States
| | - David P Ballou
- ‡Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Steven E Rokita
- †Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States.,§Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
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