1
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Schroeder L, Diepold N, Gäfe S, Niemann HH, Kottke T. Coupling and regulation mechanisms of the flavin-dependent halogenase PyrH observed by infrared difference spectroscopy. J Biol Chem 2024; 300:107210. [PMID: 38519030 PMCID: PMC11021962 DOI: 10.1016/j.jbc.2024.107210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Revised: 02/29/2024] [Accepted: 03/15/2024] [Indexed: 03/24/2024] Open
Abstract
Flavin-dependent halogenases are central enzymes in the production of halogenated secondary metabolites in various organisms and they constitute highly promising biocatalysts for regioselective halogenation. The mechanism of these monooxygenases includes formation of hypohalous acid from a reaction of fully reduced flavin with oxygen and halide. The hypohalous acid then diffuses via a tunnel to the substrate-binding site for halogenation of tryptophan and other substrates. Oxidized flavin needs to be reduced for regeneration of the enzyme, which can be performed in vitro by a photoreduction with blue light. Here, we employed this photoreduction to study characteristic structural changes associated with the transition from oxidized to fully reduced flavin in PyrH from Streptomyces rugosporus as a model for tryptophan-5-halogenases. The effect of the presence of bromide and chloride or the absence of any halides on the UV-vis spectrum of the enzyme demonstrated a halide-dependent structure of the flavin-binding pocket. Light-induced FTIR difference spectroscopy was applied and the signals assigned by selective isotope labeling of the protein moiety. The identified structural changes in α-helix and β-sheet elements were strongly dependent on the presence of bromide, chloride, the substrate tryptophan, and the product 5-chloro-tryptophan, respectively. We identified a clear allosteric coupling in solution at ambient conditions between cofactor-binding site and substrate-binding site that is active in both directions, despite their separation by a tunnel. We suggest that this coupling constitutes a fine-tuned mechanism for the promotion of the enzymatic reaction of flavin-dependent halogenases in dependence of halide and substrate availability.
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Affiliation(s)
- Lea Schroeder
- Biophysical Chemistry and Diagnostics, Department of Chemistry, Bielefeld University, Bielefeld, Germany
| | - Niklas Diepold
- Biophysical Chemistry and Diagnostics, Department of Chemistry, Bielefeld University, Bielefeld, Germany; Biophysical Chemistry and Diagnostics, Medical School OWL, Bielefeld University, Bielefeld, Germany
| | - Simon Gäfe
- Biophysical Chemistry and Diagnostics, Department of Chemistry, Bielefeld University, Bielefeld, Germany
| | - Hartmut H Niemann
- Structural Biochemistry, Department of Chemistry, Bielefeld University, Bielefeld, Germany
| | - Tilman Kottke
- Biophysical Chemistry and Diagnostics, Department of Chemistry, Bielefeld University, Bielefeld, Germany; Biophysical Chemistry and Diagnostics, Medical School OWL, Bielefeld University, Bielefeld, Germany.
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2
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Montua N, Thye P, Hartwig P, Kühle M, Sewald N. Enzymatic Peptide and Protein Bromination: The BromoTrp Tag. Angew Chem Int Ed Engl 2024; 63:e202314961. [PMID: 38009455 DOI: 10.1002/anie.202314961] [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] [Revised: 11/21/2023] [Accepted: 11/24/2023] [Indexed: 11/28/2023]
Abstract
Bio-orthogonal reactions for modification of proteins and unprotected peptides are of high value in chemical biology. The combination of enzymatic halogenation with transition metal-catalyzed cross-coupling provides a feasible approach for the modification of proteins and unprotected peptides. By a semirational protein engineering approach, variants of the tryptophan 6-halogenase Thal were identified that enable efficient bromination of peptides with a C-terminal tryptophan residue. The substrate scope was explored using di-, tri-, and tetrapeptide arrays, leading to the identification of an optimized peptide tag we named BromoTrp tag. This tag was introduced into three model proteins. Preparative scale post-translational bromination was possible with only a single cultivation and purification step using the brominating E. coli coexpression system Brocoli. Palladium-catalyzed Suzuki-Miyaura cross-coupling of the bromoarene was achieved with Pd nanoparticle catalysts at 37 °C, highlighting the rich potential of this strategy for bio-orthogonal functionalization and conjugation.
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Affiliation(s)
- Nicolai Montua
- Organic and Bioorganic Chemistry, Department of Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Paula Thye
- Organic and Bioorganic Chemistry, Department of Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Pia Hartwig
- Organic and Bioorganic Chemistry, Department of Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Matthias Kühle
- Organic and Bioorganic Chemistry, Department of Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Norbert Sewald
- Organic and Bioorganic Chemistry, Department of Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
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3
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Besse C, Niemann HH, Sewald N. Increasing the Stability of Flavin-Dependent Halogenases by Disulfide Engineering. Chembiochem 2024; 25:e202300700. [PMID: 37917145 DOI: 10.1002/cbic.202300700] [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: 10/13/2023] [Revised: 10/27/2023] [Accepted: 11/02/2023] [Indexed: 11/03/2023]
Abstract
Flavin-dependent halogenases allow halogenation of electron-rich aromatic compounds under mild reaction conditions even at electronically unfavored positions with high regioselectivity. In order to expand the application of halogenases, the enzymes need to be improved in terms of stability and efficiency. A previous study with the tryptophan 6-halogenase Thal demonstrated that thermostable Thal variants tend to form dimers in solution while the wild type is present as a monomer. Based on this a dimeric Thal variant was generated that is covalently linked by disulfide bonds. Introducing two cysteine residues at the dimer interface resulted in the variant Thal CC with significantly increased thermostability (▵T50 =15.7 K) and stability over time at elevated temperature compared to the wild type. By introducing the homologous mutations into the tryptophan 5-halogenase PyrH, we were able to show that the stabilization by covalent dimerization can also be transferred to other halogenases. Moreover, it was possible to further increase the thermostability of PyrH by inserting cysteine mutations at alternative sites of the dimer interface.
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Affiliation(s)
- Caroline Besse
- Organic and Bioorganic Chemistry, Department of Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Hartmut H Niemann
- Structural Biochemistry, Department of Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Norbert Sewald
- Organic and Bioorganic Chemistry, Department of Chemistry, Bielefeld University, Universitätsstraße 25, 33615, Bielefeld, Germany
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4
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Ashaduzzaman M, Lingkon K, De Silva AJ, Bellizzi JJ. Crystallographic and thermodynamic evidence of negative cooperativity of flavin and tryptophan binding in the flavin-dependent halogenases AbeH and BorH. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.22.554356. [PMID: 37662313 PMCID: PMC10473636 DOI: 10.1101/2023.08.22.554356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
The flavin-dependent halogenase AbeH produces 5-chlorotryptophan in the biosynthetic pathway of the chlorinated bisindole alkaloid BE-54017. We report that in vitro, AbeH (assisted by the flavin reductase AbeF) can chlorinate and brominate tryptophan as well as other indole derivatives and substrates with phenyl and quinoline groups. We solved the X-ray crystal structures of AbeH alone and complexed with FAD, as well as crystal structures of the tryptophan-6-halogenase BorH alone, in complex with 6-chlorotryptophan, and in complex with FAD and tryptophan. Partitioning of FAD and tryptophan into different chains of BorH and failure to incorporate tryptophan into AbeH/FAD crystals suggested that flavin and tryptophan binding are negatively coupled in both proteins. ITC and fluorescence quenching experiments confirmed the ability of both AbeH and BorH to form binary complexes with FAD or tryptophan and the inability of tryptophan to bind to AbeH/FAD or BorH/FAD complexes. FAD could not bind to BorH/tryptophan complexes, but FAD appears to displace tryptophan from AbeH/tryptophan complexes in an endothermic entropically-driven process.
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Affiliation(s)
- Md Ashaduzzaman
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo OH 43606
| | - Kazi Lingkon
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo OH 43606
| | - Aravinda J De Silva
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo OH 43606
| | - John J Bellizzi
- Department of Chemistry and Biochemistry, The University of Toledo, Toledo OH 43606
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5
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Schnepel C, Moritzer AC, Gäfe S, Montua N, Minges H, Nieß A, Niemann HH, Sewald N. Enzymatic Late-Stage Halogenation of Peptides. Chembiochem 2023; 24:e202200569. [PMID: 36259362 PMCID: PMC10099709 DOI: 10.1002/cbic.202200569] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 10/18/2022] [Indexed: 01/05/2023]
Abstract
The late-stage site-selective derivatisation of peptides has many potential applications in structure-activity relationship studies and postsynthetic modification or conjugation of bioactive compounds. The development of orthogonal methods for C-H functionalisation is crucial for such peptide derivatisation. Among them, biocatalytic methods are increasingly attracting attention. Tryptophan halogenases emerged as valuable catalysts to functionalise tryptophan (Trp), while direct enzyme-catalysed halogenation of synthetic peptides is yet unprecedented. Here, it is reported that the Trp 6-halogenase Thal accepts a wide range of amides and peptides containing a Trp moiety. Increasing the sequence length and reaction optimisation made bromination of pentapeptides feasible with good turnovers and a broad sequence scope, while regioselectivity turned out to be sequence dependent. Comparison of X-ray single crystal structures of Thal in complex with d-Trp and a dipeptide revealed a significantly altered binding mode for the peptide. The viability of this bioorthogonal approach was exemplified by halogenation of a cyclic RGD peptide.
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Affiliation(s)
- Christian Schnepel
- Organische und Bioorganische Chemie, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, 33615, Bielefeld, Germany.,Present address: Department of Chemistry, Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK
| | - Ann-Christin Moritzer
- Strukturbiochemie, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Simon Gäfe
- Strukturbiochemie, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Nicolai Montua
- Organische und Bioorganische Chemie, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Hannah Minges
- Organische und Bioorganische Chemie, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Anke Nieß
- Organische und Bioorganische Chemie, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Hartmut H Niemann
- Strukturbiochemie, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, 33615, Bielefeld, Germany
| | - Norbert Sewald
- Organische und Bioorganische Chemie, Fakultät für Chemie, Universität Bielefeld, Universitätsstraße 25, 33615, Bielefeld, Germany
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6
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Jiang Y, Snodgrass HM, Zubi YS, Roof CV, Guan Y, Mondal D, Honeycutt NH, Lee JW, Lewis RD, Martinez CA, Lewis JC. The Single-Component Flavin Reductase/Flavin-Dependent Halogenase AetF is a Versatile Catalyst for Selective Bromination and Iodination of Arenes and Olefins. Angew Chem Int Ed Engl 2022; 61:e202214610. [PMID: 36282507 PMCID: PMC9772203 DOI: 10.1002/anie.202214610] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Indexed: 11/05/2022]
Abstract
Flavin-dependent halogenases (FDHs) natively catalyze selective halogenation of electron rich aromatic and enolate groups. Nearly all FDHs reported to date require a separate flavin reductase to supply them with FADH2 , which complicates biocatalysis applications. In this study, we establish that the single component flavin reductase/flavin dependent halogenase AetF catalyzes halogenation of a diverse set of substrates using a commercially available glucose dehydrogenase to drive its halogenase activity. High site selectivity, activity on relatively unactivated substrates, and high enantioselectivity for atroposelective bromination and bromolactonization was demonstrated. Site-selective iodination and enantioselective cycloiodoetherification was also possible using AetF. The substrate and reaction scope of AetF suggest that it has the potential to greatly improve the utility of biocatalytic halogenation.
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Affiliation(s)
- Yuhua Jiang
- Department of ChemistryIndiana UniversityBloomingtonIN 47405USA
| | | | - Yasmine S. Zubi
- Department of ChemistryIndiana UniversityBloomingtonIN 47405USA
| | - Caitlin V. Roof
- Department of ChemistryIndiana UniversityBloomingtonIN 47405USA
| | - Yanfei Guan
- Chemical Research & DevelopmentPfizer Worldwide Research & DevelopmentGrotonConnecticut 06340USA
| | - Dibyendu Mondal
- Department of ChemistryIndiana UniversityBloomingtonIN 47405USA
- Kalsec Inc.3713W. Main St.KalamazooMichigan 49006USA
| | | | - Johnny W. Lee
- Chemical Research & DevelopmentPfizer Worldwide Research & DevelopmentGrotonConnecticut 06340USA
| | - Russell D. Lewis
- Chemical Research & DevelopmentPfizer Worldwide Research & DevelopmentGrotonConnecticut 06340USA
| | - Carlos A. Martinez
- Chemical Research & DevelopmentPfizer Worldwide Research & DevelopmentGrotonConnecticut 06340USA
| | - Jared C. Lewis
- Department of ChemistryIndiana UniversityBloomingtonIN 47405USA
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7
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Barker RD, Yu Y, De Maria L, Johannissen LO, Scrutton NS. Mechanism of Action of Flavin-Dependent Halogenases. ACS Catal 2022; 12:15352-15360. [PMID: 36570077 PMCID: PMC9764358 DOI: 10.1021/acscatal.2c05231] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2022] [Revised: 11/12/2022] [Indexed: 12/05/2022]
Abstract
To rationally engineer the substrate scope and selectivity of flavin-dependent halogenases (FDHs), it is essential to first understand the reaction mechanism and substrate interactions in the active site. FDHs have long been known to achieve regioselectivity through an electrophilic aromatic substitution at C7 of the natural substrate Trp, but the precise role of a key active-site Lys residue remains ambiguous. Formation of hypochlorous acid (HOCl) at the cofactor-binding site is achieved by the direct reaction of molecular oxygen and a single chloride ion with reduced FAD and flavin hydroxide, respectively. HOCl is then guided 10 Å into the halogenation active site. Lys79, located in this site, has been proposed to direct HOCl toward Trp C7 through hydrogen bonding or a direct reaction with HOCl to form an -NH2Cl+ intermediate. Here, we present the most likely mechanism for halogenation based on molecular dynamics (MD) simulations and active-site density functional theory "cluster" models of FDH PrnA in complex with its native substrate l-tryptophan, hypochlorous acid, and the FAD cofactor. MD simulations with different protonation states for key active-site residues suggest that Lys79 directs HOCl through hydrogen bonding, which is confirmed by calculations of the reaction profiles for both proposed mechanisms.
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Affiliation(s)
- Rhys D. Barker
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
| | - Yuqi Yu
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
| | - Leonardo De Maria
- Research
and Early Development, Respiratory & Immunology, BioPharmaceuticals
R&D, AstraZeneca, Gothenburg 43283, Sweden
| | - Linus O. Johannissen
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.,
| | - Nigel S. Scrutton
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.,
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8
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Crowe C, Molyneux S, Sharma SV, Zhang Y, Gkotsi DS, Connaris H, Goss RJM. Halogenases: a palette of emerging opportunities for synthetic biology-synthetic chemistry and C-H functionalisation. Chem Soc Rev 2021; 50:9443-9481. [PMID: 34368824 PMCID: PMC8407142 DOI: 10.1039/d0cs01551b] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Indexed: 12/14/2022]
Abstract
The enzymatic generation of carbon-halogen bonds is a powerful strategy used by both nature and synthetic chemists to tune the bioactivity, bioavailability and reactivity of compounds, opening up the opportunity for selective C-H functionalisation. Genes encoding halogenase enzymes have recently been shown to transcend all kingdoms of life. These enzymes install halogen atoms into aromatic and less activated aliphatic substrates, achieving selectivities that are often challenging to accomplish using synthetic methodologies. Significant advances in both halogenase discovery and engineering have provided a toolbox of enzymes, enabling the ready use of these catalysts in biotransformations, synthetic biology, and in combination with chemical catalysis to enable late stage C-H functionalisation. With a focus on substrate scope, this review outlines the mechanisms employed by the major classes of halogenases, while in parallel, it highlights key advances in the utilisation of the combination of enzymatic halogenation and chemical catalysis for C-H activation and diversification.
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Affiliation(s)
- Charlotte Crowe
- School of Chemistry, and BSRC, University of St Andrews, North HaughSt Andrews KY16 9STUK
| | - Samuel Molyneux
- School of Chemistry, and BSRC, University of St Andrews, North HaughSt Andrews KY16 9STUK
| | - Sunil V. Sharma
- School of Chemistry, and BSRC, University of St Andrews, North HaughSt Andrews KY16 9STUK
| | - Ying Zhang
- School of Chemistry, and BSRC, University of St Andrews, North HaughSt Andrews KY16 9STUK
| | - Danai S. Gkotsi
- School of Chemistry, and BSRC, University of St Andrews, North HaughSt Andrews KY16 9STUK
| | - Helen Connaris
- School of Chemistry, and BSRC, University of St Andrews, North HaughSt Andrews KY16 9STUK
| | - Rebecca J. M. Goss
- School of Chemistry, and BSRC, University of St Andrews, North HaughSt Andrews KY16 9STUK
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9
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Geerds C, Haas A, Niemann HH. Conformational changes of loops highlight a potential binding site in Rhodococcus equi VapB. Acta Crystallogr F Struct Biol Commun 2021; 77:246-253. [PMID: 34341190 PMCID: PMC8329714 DOI: 10.1107/s2053230x2100738x] [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: 05/11/2021] [Accepted: 07/16/2021] [Indexed: 12/04/2022] Open
Abstract
Virulence-associated proteins (Vaps) contribute to the virulence of the pathogen Rhodococcus equi, but their mode of action has remained elusive. All Vaps share a conserved core of about 105 amino acids that folds into a compact eight-stranded antiparallel β-barrel with a unique topology. At the top of the barrel, four loops connect the eight β-strands. Previous Vap structures did not show concave surfaces that might serve as a ligand-binding site. Here, the structure of VapB in a new crystal form was determined at 1.71 Å resolution. The asymmetric unit contains two molecules. In one of them, the loop regions at the top of the barrel adopt a different conformation from other Vap structures. An outward movement of the loops results in the formation of a hydrophobic cavity that might act as a ligand-binding site. This lends further support to the hypothesis that the structural similarity between Vaps and avidins suggests a potential binding function for Vaps.
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Affiliation(s)
- Christina Geerds
- Department of Chemistry, Bielefeld University, Universitaetsstrasse 25, 33615 Bielefeld, Germany
| | - Albert Haas
- Institute for Cell Biology, University of Bonn, Ulrich-Haberland-Strasse 61a, 53121 Bonn, Germany
| | - Hartmut H. Niemann
- Department of Chemistry, Bielefeld University, Universitaetsstrasse 25, 33615 Bielefeld, Germany
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10
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Genomic Determinants Encode the Reactivity and Regioselectivity of Flavin-Dependent Halogenases in Bacterial Genomes and Metagenomes. mSystems 2021; 6:e0005321. [PMID: 34042468 PMCID: PMC8269204 DOI: 10.1128/msystems.00053-21] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Halogenases create diverse natural products by utilizing halide ions and are of great interest in the synthesis of potential pharmaceuticals and agrochemicals. An increasing number of halogenases discovered in microorganisms are annotated as flavin-dependent halogenases (FDHs), but their chemical reactivities are markedly different and the genomic contents associated with such functional distinction have not been revealed yet. Even though the reactivity and regioselectivity of FDHs are essential in the halogenation activity, these FDHs are annotated inaccurately in the protein sequence repositories without characterizing their functional activities. We carried out a comprehensive sequence analysis and biochemical characterization of FDHs. Using a probabilistic model that we built in this study, FDHs were discovered from 2,787 bacterial genomes and 17 sediment metagenomes. We analyzed the essential genomic determinants that are responsible for substrate binding and subsequent reactions: four flavin adenine dinucleotide-binding, one halide-binding, and four tryptophan-binding sites. Compared with previous studies, our study utilizes large-scale genomic information to propose a comprehensive set of sequence motifs that are related to the active sites and regioselectivity. We reveal that the genomic patterns and phylogenetic locations of the FDHs determine the enzymatic reactivities, which was experimentally validated in terms of the substrate scope and regioselectivity. A large portion of publicly available FDHs needs to be reevaluated to designate their correct functions. Our genomic models establish comprehensive links among genotypic information, reactivity, and regioselectivity of FDHs, thereby laying an important foundation for future discovery and classification of novel FDHs. IMPORTANCE Halogenases are playing an important role as tailoring enzymes in biosynthetic pathways. Flavin-dependent tryptophan halogenases (Trp-FDHs) are among the enzymes that have broad substrate scope and high selectivity. From bacterial genomes and metagenomes, we found highly diverse halogenase sequences by using a well-trained profile hidden Markov model built from the experimentally validated halogenases. The characterization of genotype, steady-state activity, substrate scope, and regioselectivity has established comprehensive links between the information encoded in the genomic sequence and reactivity of FDHs reported here. By constructing models for accurate and detailed sequence markers, our work should guide future discovery and classification of novel FDHs.
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11
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Phintha A, Prakinee K, Jaruwat A, Lawan N, Visitsatthawong S, Kantiwiriyawanitch C, Songsungthong W, Trisrivirat D, Chenprakhon P, Mulholland A, van Pée KH, Chitnumsub P, Chaiyen P. Dissecting the low catalytic capability of flavin-dependent halogenases. J Biol Chem 2021; 296:100068. [PMID: 33465708 PMCID: PMC7948982 DOI: 10.1074/jbc.ra120.016004] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 11/11/2020] [Accepted: 11/13/2020] [Indexed: 12/11/2022] Open
Abstract
Although flavin-dependent halogenases (FDHs) are attractive biocatalysts, their practical applications are limited because of their low catalytic efficiency. Here, we investigated the reaction mechanisms and structures of tryptophan 6-halogenase (Thal) from Streptomyces albogriseolus using stopped-flow, rapid-quench flow, quantum/mechanics molecular mechanics calculations, crystallography, and detection of intermediate (hypohalous acid [HOX]) liberation. We found that the key flavin intermediate, C4a-hydroperoxyflavin (C4aOOH-FAD), formed by Thal and other FDHs (tryptophan 7-halogenase [PrnA] and tryptophan 5-halogenase [PyrH]), can react with I-, Br-, and Cl- but not F- to form C4a-hydroxyflavin and HOX. Our experiments revealed that I- reacts with C4aOOH-FAD the fastest with the lowest energy barrier and have shown for the first time that a significant amount of the HOX formed leaks out as free HOX. This leakage is probably a major cause of low product coupling ratios in all FDHs. Site-saturation mutagenesis of Lys79 showed that changing Lys79 to any other amino acid resulted in an inactive enzyme. However, the levels of liberated HOX of these variants are all similar, implying that Lys79 probably does not form a chloramine or bromamine intermediate as previously proposed. Computational calculations revealed that Lys79 has an abnormally lower pKa compared with other Lys residues, implying that the catalytic Lys may act as a proton donor in catalysis. Analysis of new X-ray structures of Thal also explains why premixing of FDHs with reduced flavin adenine dinucleotide generally results in abolishment of C4aOOH-FAD formation. These findings reveal the hidden factors restricting FDHs capability which should be useful for future development of FDHs applications.
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Affiliation(s)
- Aisaraphon Phintha
- Department of Biochemistry and Center for Excellence in Protein and Enzyme Technology, Faculty of Science, Mahidol University, Bangkok, Thailand; School of Biomolecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC), Rayong, Thailand
| | - Kridsadakorn Prakinee
- School of Biomolecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC), Rayong, Thailand
| | - Aritsara Jaruwat
- Biomolecular Analysis and Application Research Team, National Center for Genetic Engineering and Biotechnology, Klong Luang, Pathumthani, Thailand
| | - Narin Lawan
- Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai, Thailand
| | - Surawit Visitsatthawong
- School of Biomolecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC), Rayong, Thailand
| | - Chadaporn Kantiwiriyawanitch
- School of Biomolecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC), Rayong, Thailand
| | - Warangkhana Songsungthong
- Biomolecular Analysis and Application Research Team, National Center for Genetic Engineering and Biotechnology, Klong Luang, Pathumthani, Thailand
| | - Duangthip Trisrivirat
- School of Biomolecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC), Rayong, Thailand
| | - Pirom Chenprakhon
- Institute for Innovative Learning, Mahidol University, Nakhon Pathom, Thailand
| | - Adrian Mulholland
- Centre for Computational Chemistry, School of Chemistry, University of Bristol, Bristol, UK
| | - Karl-Heinz van Pée
- General Biochemistry, Faculty of Chemistry and Food Chemistry, Technical University of Dresden, Dresden, Germany
| | - Penchit Chitnumsub
- Biomolecular Analysis and Application Research Team, National Center for Genetic Engineering and Biotechnology, Klong Luang, Pathumthani, Thailand.
| | - Pimchai Chaiyen
- Department of Biochemistry and Center for Excellence in Protein and Enzyme Technology, Faculty of Science, Mahidol University, Bangkok, Thailand; School of Biomolecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC), Rayong, Thailand.
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12
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Neubauer PR, Pienkny S, Wessjohann L, Brandt W, Sewald N. Predicting the Substrate Scope of the Flavin-Dependent Halogenase BrvH. Chembiochem 2020; 21:3282-3288. [PMID: 32645255 PMCID: PMC7754283 DOI: 10.1002/cbic.202000444] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Indexed: 01/16/2023]
Abstract
The recently described flavin-dependent halogenase BrvH is able to catalyse both the bromination and chlorination of indole, but shows significantly higher bromination activity. BrvH was annotated as a tryptophan halogenase, but does not accept tryptophan as a substrate. Its native substrate remains unknown. A predictive model with the data available for BrvH was analysed. A training set of compounds tested in vitro was docked into the active site of a complete protein model based on the X-ray structure of BrvH. The atoms not resolved experimentally were modelled by using molecular mechanics force fields to obtain this protein model. Furthermore, docking poses for the substrates and known non-substrates have been calculated. Parameters like distance, partial charge and hybridization state were analysed to derive rules for predicting activity. With this model for activity of the BrvH, a virtual screening suggested several structures for potential substrates. Some of the compounds preselected in this way were tested in vitro, and several could be verified as convertible substrates. Based on information on halogenated natural products, a new dataset was created to specifically search for natural products as substrates/products, and virtual screening in this database yielded further hits.
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Affiliation(s)
- Pia R. Neubauer
- Organic and Bioorganic ChemistryDepartment of ChemistryBielefeld UniversityUniversitätsstrasse 2533501BielefeldGermany
| | - Silke Pienkny
- Leibniz Institute for Plant Biochemistry (IPB)Weinberg 306120HalleGermany
| | - Ludger Wessjohann
- Leibniz Institute for Plant Biochemistry (IPB)Weinberg 306120HalleGermany
| | - Wolfgang Brandt
- Leibniz Institute for Plant Biochemistry (IPB)Weinberg 306120HalleGermany
| | - Norbert Sewald
- Organic and Bioorganic ChemistryDepartment of ChemistryBielefeld UniversityUniversitätsstrasse 2533501BielefeldGermany
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Flavin Adenine Dinucleotide-Dependent Halogenase XanH and Engineering of Multifunctional Fusion Halogenases. Appl Environ Microbiol 2020; 86:AEM.01225-20. [PMID: 32651204 DOI: 10.1128/aem.01225-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Accepted: 07/02/2020] [Indexed: 12/19/2022] Open
Abstract
Xantholipin (compound 1), a polycyclic xanthone antibiotic, exhibited strong antibacterial activities and showed potent cytotoxicity. The biosynthetic gene cluster of compound 1 has been identified in our previous work, and the construction of xanthone nucleus has been well demonstrated. However, limited information of the halogenation involved in compound 1 biosynthesis is available. In this study, based on the genetic manipulation and biochemical assay, we characterized XanH as an indispensable flavin adenine dinucleotide (FAD)-dependent halogenase (FDH) for the biosynthesis of compound 1. XanH was found to be a bifunctional protein capable of flavin reduction and chlorination and exclusively used the NADH. However, the reduced flavin could not be fully and effectively utilized, and the presence of an extra flavin reductase (FDR) and chemical-reducing agent could promote the halogenation. XanH accepted its natural free-standing substrate with angular fused polycyclic aromatic systems. Meanwhile, it exhibited moderate halogenation activity and possessed high substrate specificity. The requirement of extra FDR for higher halogenation activity is tedious for future engineering. To facilitate efforts in engineering XanH derivative proteins, we constructed the self-sufficient FDR-XanH fusion proteins. The fusion protein E1 with comparable activities to that of XanH could be used as a good alternative for future protein engineering. Taken together, these findings reported here not only improve the understanding of polycyclic xanthones biosynthesis but also expand the substrate scope of FDH and pave the way for future engineering of biocatalysts for new active substance synthesis.IMPORTANCE Halogenation is important in medicinal chemistry and plays an essential role in the biosynthesis of active secondary metabolites. Halogenases have evolved to catalyze reactions with high efficiency and selectivity, and engineering efforts have been made to engage the selective reactivity in natural product biosynthesis. The enzymatic halogenations are an environmentally friendly approach with high regio- and stereoselectivity, which make it a potential complement to organic synthesis. FDHs constitute one of the most extensively elucidated class of halogenases; however, the inventory awaits to be expanded for biotechnology applications and for the generation of halogenated natural product analogues. In this study, XanH was found to reduce flavin and halogenated the freely diffusing natural substrate with an angular fused hexacyclic scaffold, findings which were different from those for the exclusively studied FDHs. Moreover, the FDR-XanH fusion protein E1 with comparable reactivity to that of XanH serves as a successful example of genetic fusions and sets an important stage for future protein engineering.
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Minges H, Sewald N. Recent Advances in Synthetic Application and Engineering of Halogenases. ChemCatChem 2020. [DOI: 10.1002/cctc.202000531] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Hannah Minges
- Organic and Bioorganic Chemistry Department of Chemistry Bielefeld University Universitätsstraße 25 33501 Bielefeld Germany
| | - Norbert Sewald
- Organic and Bioorganic Chemistry Department of Chemistry Bielefeld University Universitätsstraße 25 33501 Bielefeld Germany
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15
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Abstract
Overall, this review highlights the structures, mechanisms and applications of flavin-dependent halogenases (FDHs) for future development of FDHs as potential biocatalysts. FDHs catalyze incorporation of halogen atoms into a broad range of substrates. The reactions involved in the production of various halogenated natural products which are important drugs. Typical substrates for FDHs include indole, pyrrole, phenolic and aliphatic compounds. In addition to organic substrates, all FDHs utilize reduced FAD (FADH-), oxygen and halides as co-substrates. Structural studies reveal that FDHs all have similar FAD binding sites. However, FDHs have variations between the different isotypes including different recognition residues for substrate binding and some unique loop structures and conformations. These different structural differences suggest that variations in reaction catalysis exist. However, limited knowledge of the reaction mechanisms of FDHs is currently available. Various biocatalytic applications of FDHs have been explored. Further investigation of the catalytic reactions of FDHs is essential for improving enzyme engineering work to enable FDHs catalysis of challenging reactions.
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Affiliation(s)
- Aisaraphon Phintha
- Department of Biochemistry and Center for Excellence in Protein and Enzyme Technology, Faculty of Science, Mahidol University, Bangkok, Thailand
| | - Kridsadakorn Prakinee
- School of Biomolecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC), Wangchan Valley, Rayong, Thailand
| | - Pimchai Chaiyen
- School of Biomolecular Science and Engineering, Vidyasirimedhi Institute of Science and Technology (VISTEC), Wangchan Valley, Rayong, Thailand.
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Widmann C, Ismail M, Sewald N, Niemann HH. Structure of apo flavin-dependent halogenase Xcc4156 hints at a reason for cofactor-soaking difficulties. Acta Crystallogr D Struct Biol 2020; 76:687-697. [PMID: 32627741 PMCID: PMC7336383 DOI: 10.1107/s2059798320007731] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 06/05/2020] [Indexed: 01/18/2023] Open
Abstract
Flavin-dependent halogenases regioselectively introduce halide substituents into electron-rich substrates under mild reaction conditions. For the enzyme Xcc4156 from Xanthomonas campestris, the structure of a complex with the cofactor flavin adenine dinucleotide (FAD) and a bromide ion would be of particular interest as this enzyme exclusively brominates model substrates in vitro. Apo Xcc4156 crystals diffracted to 1.6 Å resolution. The structure revealed an open substrate-binding site lacking the loop regions that close off the active site and contribute to substrate binding in tryptophan halogenases. Therefore, Xcc4156 might accept larger substrates, possibly even peptides. Soaking of apo Xcc4156 crystals with FAD led to crumbling of the intergrown crystals. Around half of the crystals soaked with FAD did not diffract, while in the others there was no electron density for FAD. The FAD-binding loop, which changes its conformation between the apo and the FAD-bound form in related enzymes, is involved in a crystal contact in the apo Xcc4156 crystals. The conformational change that is predicted to occur upon FAD binding would disrupt this crystal contact, providing a likely explanation for the destruction of the apo crystals in the presence of FAD. Soaking with only bromide did not result in bromide bound to the catalytic halide-binding site. Simultaneous soaking with FAD and bromide damaged the crystals more severely than soaking with only FAD. Together, these latter two observations suggest that FAD and bromide bind to Xcc4156 with positive cooperativity. Thus, apo Xcc4156 crystals provide functional insight into FAD and bromide binding, even though neither the cofactor nor the halide is visible in the structure.
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Affiliation(s)
- Christiane Widmann
- Structural Biochemistry (BCIV), Department of Chemistry, Bielefeld University, Universitaetsstrasse 25, 33615 Bielefeld, Germany
| | - Mohamed Ismail
- Organic and Bioorganic Chemistry (OC III), Department of Chemistry, Bielefeld University, Universitaetsstrasse 25, 33615 Bielefeld, Germany
| | - Norbert Sewald
- Organic and Bioorganic Chemistry (OC III), Department of Chemistry, Bielefeld University, Universitaetsstrasse 25, 33615 Bielefeld, Germany
| | - Hartmut H. Niemann
- Structural Biochemistry (BCIV), Department of Chemistry, Bielefeld University, Universitaetsstrasse 25, 33615 Bielefeld, Germany
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Moritzer A, Niemann HH. Binding of FAD and tryptophan to the tryptophan 6-halogenase Thal is negatively coupled. Protein Sci 2019; 28:2112-2118. [PMID: 31589794 PMCID: PMC6863734 DOI: 10.1002/pro.3739] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Revised: 09/27/2019] [Accepted: 09/30/2019] [Indexed: 11/08/2022]
Abstract
Flavin-dependent halogenases require reduced flavin adenine dinucleotide (FADH2 ), O2 , and halide salts to halogenate their substrates. We describe the crystal structures of the tryptophan 6-halogenase Thal in complex with FAD or with both tryptophan and FAD. If tryptophan and FAD were soaked simultaneously, both ligands showed impaired binding and in some cases only the adenosine monophosphate or the adenosine moiety of FAD was resolved, suggesting that tryptophan binding increases the mobility mainly of the flavin mononucleotide moiety. This confirms a negative cooperativity between the binding of substrate and cofactor that was previously described for other tryptophan halogenases. Binding of substrate to tryptophan halogenases reduces the affinity for the oxidized cofactor FAD presumably to facilitate the regeneration of FADH2 by flavin reductases.
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