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Barber V, Mielke T, Cartwright J, Díaz-Rodríguez A, Unsworth WP, Grogan G. Unspecific Peroxygenase (UPO) can be Tuned for Oxygenation or Halogenation Activity by Controlling the Reaction pH. Chemistry 2024:e202401706. [PMID: 38700372 DOI: 10.1002/chem.202401706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2024] [Revised: 05/02/2024] [Accepted: 05/03/2024] [Indexed: 05/05/2024]
Abstract
Unspecific Peroxygenases (UPOs) are increasingly significant enzymes for selective oxygenations as they are stable, highly active and catalyze their reactions at the expense of only hydrogen peroxide as the oxidant. Their structural similarity to chloroperoxidase (CPO) means that UPOs can also catalyze halogenation reactions based upon the generation of hypohalous acids from halide and H2O2. Here we show that the halogenation and oxygenation modes of a UPO can be stimulated at different pH values. Using simple aromatic compounds such as thymol, we show that, at a pH of 3.0 and 6.0, either brominated or oxygenated products respectively are produced. Preparative 100 mg scale transformations of substrates were performed with 60-72% isolated yields of brominated products obtained. A one-pot bromination-oxygenation cascade reaction on 4-ethylanisole, in which the pH was adjusted from 3.0 to 6.0 at the halfway stage, yielded sequentially brominated and oxygenated products 1-(3-bromo-4-methoxyphenyl)ethyl alcohol and 3-bromo-4-methoxy acetophenone with 82% combined conversion. These results identify UPOs as an unusual example of a biocatalyst that is tunable for entirely different chemical reactions, dependent upon the reaction conditions.
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Affiliation(s)
- Verity Barber
- University of York, Chemistry, Heslington, YO10 5DD, York, UNITED KINGDOM
| | - Tamara Mielke
- University of York, Chemistry, University of York, Heslington, Heslington, Heslington, YO10 5DD, York, UNITED KINGDOM
| | - Jared Cartwright
- University of York, Biology, University of York, Heslington, Heslington, Heslington, YO10 5DD, York, UNITED KINGDOM
| | - Alba Díaz-Rodríguez
- GlaxoSmithKline Research & Development Limited, Chemistry, Gunnels Wood Road, SG1 2NY, Stevenage, UNITED KINGDOM
| | - William P Unsworth
- University of York, Chemistry, University of York, Heslington, Heslington, Heslington, YO10 5DD, York, UNITED KINGDOM
| | - Gideon Grogan
- University of York Department of Chemistry, Chemistry, Heslington, YO10 5DD, York, UNITED KINGDOM
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2
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Pogrányi B, Mielke T, Díaz-Rodríguez A, Cartwright J, Unsworth WP, Grogan G. Preparative-Scale Biocatalytic Oxygenation of N-Heterocycles with a Lyophilized Peroxygenase Catalyst. Angew Chem Int Ed Engl 2023; 62:e202214759. [PMID: 36453718 PMCID: PMC10107140 DOI: 10.1002/anie.202214759] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Revised: 11/17/2022] [Accepted: 11/30/2022] [Indexed: 12/02/2022]
Abstract
A lyophilized preparation of an unspecific peroxygenase variant from Agrocybe aegerita (rAaeUPO-PaDa-I-H) is a highly effective catalyst for the oxygenation of a diverse range of N-heterocyclic compounds. Scalable biocatalytic oxygenations (27 preparative examples, ca. 100 mg scale) have been developed across a wide range of substrates, including alkyl pyridines, bicyclic N-heterocycles and indoles. H2 O2 is the only stoichiometric oxidant needed, without auxiliary electron transport proteins, which is key to the practicality of the method. Reaction outcomes can be altered depending on whether hydrogen peroxide was delivered by syringe pump or through in situ generation using an alcohol oxidase from Pichia pastoris (PpAOX) and methanol as a co-substrate. Good synthetic yields (up to 84 %), regioselectivity and enantioselectivity (up to 99 % ee) were observed in some cases, highlighting the promise of UPOs as practical, versatile and scalable oxygenation biocatalysts.
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Affiliation(s)
- Balázs Pogrányi
- Department of Chemistry, University of York, Heslington York, YO10 5DD, UK
| | - Tamara Mielke
- Department of Chemistry, University of York, Heslington York, YO10 5DD, UK
| | - Alba Díaz-Rodríguez
- GSK Medicines Research Centre, Gunnels Wood Road, Stevenage, Hertfordshire, SG1 2NY, UK
| | - Jared Cartwright
- Department of Biology, University of York, Heslington York, YO10 5DD, UK
| | - William P Unsworth
- Department of Chemistry, University of York, Heslington York, YO10 5DD, UK
| | - Gideon Grogan
- Department of Chemistry, University of York, Heslington York, YO10 5DD, UK
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3
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Robinson WXQ, Mielke T, Melling B, Cuetos A, Parkin A, Unsworth WP, Cartwright J, Grogan G. Comparing the Catalytic and Structural Characteristics of a 'Short' Unspecific Peroxygenase (UPO) Expressed in Pichia pastoris and Escherichia coli. Chembiochem 2023; 24:e202200558. [PMID: 36374006 PMCID: PMC10098773 DOI: 10.1002/cbic.202200558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 11/14/2022] [Indexed: 11/16/2022]
Abstract
Unspecific peroxygenases (UPOs) have emerged as valuable tools for the oxygenation of non-activated carbon atoms, as they exhibit high turnovers, good stability and depend only on hydrogen peroxide as the external oxidant for activity. However, the isolation of UPOs from their natural fungal sources remains a barrier to wider application. We have cloned the gene encoding an 'artificial' peroxygenase (artUPO), close in sequence to the 'short' UPO from Marasmius rotula (MroUPO), and expressed it in both the yeast Pichia pastoris and E. coli to compare the catalytic and structural characteristics of the enzymes produced in each system. Catalytic efficiency for the UPO substrate 5-nitro-1,3-benzodioxole (NBD) was largely the same for both enzymes, and the structures also revealed few differences apart from the expected glycosylation of the yeast enzyme. However, the glycosylated enzyme displayed greater stability, as determined by nano differential scanning fluorimetry (nano-DSF) measurements. Interestingly, while artUPO hydroxylated ethylbenzene derivatives to give the (R)-alcohols, also given by a variant of the 'long' UPO from Agrocybe aegerita (AaeUPO), it gave the opposite (S)-series of sulfoxide products from a range of sulfide substrates, broadening the scope for application of the enzymes. The structures of artUPO reveal substantial differences to that of AaeUPO, and provide a platform for investigating the distinctive activity of this and related'short' UPOs.
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Affiliation(s)
- Wendy X Q Robinson
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
| | - Tamara Mielke
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
| | - Benjamin Melling
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
| | - Anibal Cuetos
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
| | - Alison Parkin
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
| | - William P Unsworth
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
| | - Jared Cartwright
- Department of Biology, University of York, Heslington, York, YO10 5DD, UK
| | - Gideon Grogan
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
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4
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Schmermund L, Reischauer S, Bierbaumer S, Winkler CK, Diaz‐Rodriguez A, Edwards LJ, Kara S, Mielke T, Cartwright J, Grogan G, Pieber B, Kroutil W. Chromoselective Photocatalysis Enables Stereocomplementary Biocatalytic Pathways*. Angew Chem Int Ed Engl 2021; 60:6965-6969. [PMID: 33529432 PMCID: PMC8048449 DOI: 10.1002/anie.202100164] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Indexed: 12/26/2022]
Abstract
Controlling the selectivity of a chemical reaction with external stimuli is common in thermal processes, but rare in visible-light photocatalysis. Here we show that the redox potential of a carbon nitride photocatalyst (CN-OA-m) can be tuned by changing the irradiation wavelength to generate electron holes with different oxidation potentials. This tuning was the key to realizing photo-chemo-enzymatic cascades that give either the (S)- or the (R)-enantiomer of phenylethanol. In combination with an unspecific peroxygenase from Agrocybe aegerita, green light irradiation of CN-OA-m led to the enantioselective hydroxylation of ethylbenzene to (R)-1-phenylethanol (99 % ee). In contrast, blue light irradiation triggered the photocatalytic oxidation of ethylbenzene to acetophenone, which in turn was enantioselectively reduced with an alcohol dehydrogenase from Rhodococcus ruber to form (S)-1-phenylethanol (93 % ee).
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Affiliation(s)
- Luca Schmermund
- Institute of ChemistryDepartment of Organic and Bioorganic ChemistryUniversity of Graz, NAWI Graz, BioTechMed GrazHeinrichstrasse 288010GrazAustria
| | - Susanne Reischauer
- Department of Biomolecular SystemsMax Planck Institute of Colloids and InterfacesAm Mühlenberg114476PotsdamGermany
| | - Sarah Bierbaumer
- Institute of ChemistryDepartment of Organic and Bioorganic ChemistryUniversity of Graz, NAWI Graz, BioTechMed GrazHeinrichstrasse 288010GrazAustria
| | - Christoph K. Winkler
- Institute of ChemistryDepartment of Organic and Bioorganic ChemistryUniversity of Graz, NAWI Graz, BioTechMed GrazHeinrichstrasse 288010GrazAustria
| | - Alba Diaz‐Rodriguez
- Chemical Development, Medicinal Science and Technology, Pharma R&DGlaxoSmithKline Medicines Research CentreGunnels Wood RoadStevenageSG1 2NYUK
| | - Lee J. Edwards
- Chemical Development, Medicinal Science and Technology, Pharma R&DGlaxoSmithKline Medicines Research CentreGunnels Wood RoadStevenageSG1 2NYUK
| | - Selin Kara
- Department of Engineering, Biological and Chemical EngineeringBiocatalysis and Bioprocessing GroupAarhus UniversityGustav Wieds Vej 108000AarhusDenmark
| | - Tamara Mielke
- Department of ChemistryUniversity of YorkHeslingtonYorkYO10 5DDUK
| | - Jared Cartwright
- Department of ChemistryUniversity of YorkHeslingtonYorkYO10 5DDUK
| | - Gideon Grogan
- Department of ChemistryUniversity of YorkHeslingtonYorkYO10 5DDUK
| | - Bartholomäus Pieber
- Department of Biomolecular SystemsMax Planck Institute of Colloids and InterfacesAm Mühlenberg114476PotsdamGermany
| | - Wolfgang Kroutil
- Institute of ChemistryDepartment of Organic and Bioorganic ChemistryUniversity of Graz, NAWI Graz, BioTechMed GrazHeinrichstrasse 288010GrazAustria
- Field of Excellence BioHealth-University of Graz8010GrazAustria
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5
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Schmermund L, Reischauer S, Bierbaumer S, Winkler CK, Diaz‐Rodriguez A, Edwards LJ, Kara S, Mielke T, Cartwright J, Grogan G, Pieber B, Kroutil W. Chromoselective Photocatalysis Enables Stereocomplementary Biocatalytic Pathways. Angew Chem Weinheim Bergstr Ger 2021; 133:7041-7045. [PMID: 38504955 PMCID: PMC10946972 DOI: 10.1002/ange.202100164] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Indexed: 12/28/2022]
Abstract
Controlling the selectivity of a chemical reaction with external stimuli is common in thermal processes, but rare in visible-light photocatalysis. Here we show that the redox potential of a carbon nitride photocatalyst (CN-OA-m) can be tuned by changing the irradiation wavelength to generate electron holes with different oxidation potentials. This tuning was the key to realizing photo-chemo-enzymatic cascades that give either the (S)- or the (R)-enantiomer of phenylethanol. In combination with an unspecific peroxygenase from Agrocybe aegerita, green light irradiation of CN-OA-m led to the enantioselective hydroxylation of ethylbenzene to (R)-1-phenylethanol (99 % ee). In contrast, blue light irradiation triggered the photocatalytic oxidation of ethylbenzene to acetophenone, which in turn was enantioselectively reduced with an alcohol dehydrogenase from Rhodococcus ruber to form (S)-1-phenylethanol (93 % ee).
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Affiliation(s)
- Luca Schmermund
- Institute of ChemistryDepartment of Organic and Bioorganic ChemistryUniversity of Graz, NAWI Graz, BioTechMed GrazHeinrichstrasse 288010GrazAustria
| | - Susanne Reischauer
- Department of Biomolecular SystemsMax Planck Institute of Colloids and InterfacesAm Mühlenberg114476PotsdamGermany
| | - Sarah Bierbaumer
- Institute of ChemistryDepartment of Organic and Bioorganic ChemistryUniversity of Graz, NAWI Graz, BioTechMed GrazHeinrichstrasse 288010GrazAustria
| | - Christoph K. Winkler
- Institute of ChemistryDepartment of Organic and Bioorganic ChemistryUniversity of Graz, NAWI Graz, BioTechMed GrazHeinrichstrasse 288010GrazAustria
| | - Alba Diaz‐Rodriguez
- Chemical Development, Medicinal Science and Technology, Pharma R&DGlaxoSmithKline Medicines Research CentreGunnels Wood RoadStevenageSG1 2NYUK
| | - Lee J. Edwards
- Chemical Development, Medicinal Science and Technology, Pharma R&DGlaxoSmithKline Medicines Research CentreGunnels Wood RoadStevenageSG1 2NYUK
| | - Selin Kara
- Department of Engineering, Biological and Chemical EngineeringBiocatalysis and Bioprocessing GroupAarhus UniversityGustav Wieds Vej 108000AarhusDenmark
| | - Tamara Mielke
- Department of ChemistryUniversity of YorkHeslingtonYorkYO10 5DDUK
| | - Jared Cartwright
- Department of ChemistryUniversity of YorkHeslingtonYorkYO10 5DDUK
| | - Gideon Grogan
- Department of ChemistryUniversity of YorkHeslingtonYorkYO10 5DDUK
| | - Bartholomäus Pieber
- Department of Biomolecular SystemsMax Planck Institute of Colloids and InterfacesAm Mühlenberg114476PotsdamGermany
| | - Wolfgang Kroutil
- Institute of ChemistryDepartment of Organic and Bioorganic ChemistryUniversity of Graz, NAWI Graz, BioTechMed GrazHeinrichstrasse 288010GrazAustria
- Field of Excellence BioHealth-University of Graz8010GrazAustria
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6
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Kölsch A, Radon C, Golub M, Baumert A, Bürger J, Mielke T, Lisdat F, Feoktystov A, Pieper J, Zouni A, Wendler P. Current limits of structural biology: The transient interaction between cytochrome c 6 and photosystem I. Curr Res Struct Biol 2020; 2:171-179. [PMID: 34235477 PMCID: PMC8244401 DOI: 10.1016/j.crstbi.2020.08.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 08/11/2020] [Accepted: 08/17/2020] [Indexed: 12/22/2022] Open
Abstract
Trimeric photosystem I from the cyanobacterium Thermosynechococcus elongatus (TePSI) is an intrinsic membrane protein, which converts solar energy into electrical energy by oxidizing the soluble redox mediator cytochrome c 6 (Cyt c 6 ) and reducing ferredoxin. Here, we use cryo-electron microscopy and small angle neutron scattering (SANS) to characterize the transient binding of Cyt c 6 to TePSI. The structure of TePSI cross-linked to Cyt c 6 was solved at a resolution of 2.9 Å and shows additional cofactors as well as side chain density for 84% of the peptide chain of subunit PsaK, revealing a hydrophobic, membrane intrinsic loop that enables binding of associated proteins. Due to the poor binding specificity, Cyt c 6 could not be localized with certainty in our cryo-EM analysis. SANS measurements confirm that Cyt c 6 does not bind to TePSI at protein concentrations comparable to those for cross-linking. However, SANS data indicate a complex formation between TePSI and the non-native mitochondrial cytochrome from horse heart (Cyt c HH ). Our study pinpoints the difficulty of identifying very small binding partners (less than 5% of the overall size) in EM structures when binding affinities are poor. We relate our results to well resolved co-structures with known binding affinities and recommend confirmatory methods for complexes with K M values higher than 20 μM.
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Affiliation(s)
- A. Kölsch
- Department of Biology, Humboldt–Universität zu Berlin, Philippstrasse 13, 10115, Berlin, Germany
| | - C. Radon
- Institute of Biochemistry and Biology, Department of Biochemistry, University of Potsdam, Karl-Liebknecht Strasse 24-25, 14476, Potsdam-Golm, Germany
| | - M. Golub
- Institute of Physics, University of Tartu, Wilhelm Ostwaldi 1, 50411, Tartu, Estonia
| | - A. Baumert
- Institute of Biochemistry and Biology, Department of Biochemistry, University of Potsdam, Karl-Liebknecht Strasse 24-25, 14476, Potsdam-Golm, Germany
| | - J. Bürger
- Max-Planck Institute for Molecular Genetics, Ihnestrasse 63-73, 14195, Berlin, Germany
- Charité, Institut für Medizinische Physik und Biophysik, Charitéplatz 1, 10117, Berlin, Germany
| | - T. Mielke
- Max-Planck Institute for Molecular Genetics, Ihnestrasse 63-73, 14195, Berlin, Germany
| | - F. Lisdat
- Institute of Applied Life Sciences, Technical University of Applied Sciences Wildau, Hochschulring 1, 15745, Wildau, Germany
| | - A. Feoktystov
- Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Lichtenbergstr. 1, 85748, Garching, Germany
| | - J. Pieper
- Institute of Physics, University of Tartu, Wilhelm Ostwaldi 1, 50411, Tartu, Estonia
| | - A. Zouni
- Department of Biology, Humboldt–Universität zu Berlin, Philippstrasse 13, 10115, Berlin, Germany
| | - P. Wendler
- Institute of Biochemistry and Biology, Department of Biochemistry, University of Potsdam, Karl-Liebknecht Strasse 24-25, 14476, Potsdam-Golm, Germany
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Bonfield HE, Mercer K, Diaz‐Rodriguez A, Cook GC, McKay BSJ, Slade P, Taylor GM, Ooi WX, Williams JD, Roberts JPM, Murphy JA, Schmermund L, Kroutil W, Mielke T, Cartwright J, Grogan G, Edwards LJ. The Right Light: De Novo Design of a Robust Modular Photochemical Reactor for Optimum Batch and Flow Chemistry. CHEMPHOTOCHEM 2019. [DOI: 10.1002/cptc.201900203] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Holly E. Bonfield
- GlaxoSmithKline Medicines Research CentreGunnels Wood Road Stevenage, Hertfordshire SG1 2NY UK
| | - Kayleigh Mercer
- GlaxoSmithKline Medicines Research CentreGunnels Wood Road Stevenage, Hertfordshire SG1 2NY UK
| | - Alba Diaz‐Rodriguez
- GlaxoSmithKline Medicines Research CentreGunnels Wood Road Stevenage, Hertfordshire SG1 2NY UK
| | - Gemma C. Cook
- GlaxoSmithKline Medicines Research CentreGunnels Wood Road Stevenage, Hertfordshire SG1 2NY UK
| | - Blandine S. J. McKay
- GlaxoSmithKline Medicines Research CentreGunnels Wood Road Stevenage, Hertfordshire SG1 2NY UK
| | - Pawel Slade
- GlaxoSmithKline Medicines Research CentreGunnels Wood Road Stevenage, Hertfordshire SG1 2NY UK
| | - George M. Taylor
- GlaxoSmithKline Medicines Research CentreGunnels Wood Road Stevenage, Hertfordshire SG1 2NY UK
| | - Wei Xiang Ooi
- GlaxoSmithKline Medicines Research CentreGunnels Wood Road Stevenage, Hertfordshire SG1 2NY UK
| | - Jason D. Williams
- GlaxoSmithKline Medicines Research CentreGunnels Wood Road Stevenage, Hertfordshire SG1 2NY UK
| | - Jack P. M. Roberts
- GlaxoSmithKline Medicines Research CentreGunnels Wood Road Stevenage, Hertfordshire SG1 2NY UK
- Department of Pure and Applied Chemistry WestCHEMUniversity of Strathclyde 295 Cathedral Street Glasgow, Scotland G1 1XL UK
| | - John A. Murphy
- Department of Pure and Applied Chemistry WestCHEMUniversity of Strathclyde 295 Cathedral Street Glasgow, Scotland G1 1XL UK
| | - Luca Schmermund
- Institute of ChemistryUniversity of Graz Harrachgasse 21/3 8010 Graz Austria
| | - Wolfgang Kroutil
- Institute of ChemistryUniversity of Graz Harrachgasse 21/3 8010 Graz Austria
| | - Tamara Mielke
- Department of ChemistryUniversity of York Heslington, York YO10 5DD UK
| | - Jared Cartwright
- Department of ChemistryUniversity of York Heslington, York YO10 5DD UK
| | - Gideon Grogan
- Department of ChemistryUniversity of York Heslington, York YO10 5DD UK
| | - Lee J. Edwards
- GlaxoSmithKline Medicines Research CentreGunnels Wood Road Stevenage, Hertfordshire SG1 2NY UK
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8
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Jensen CN, Mielke T, Farrugia JE, Frank A, Man H, Hart S, Turkenburg JP, Grogan G. Structures of the Apo and FAD-bound forms of 2-hydroxybiphenyl 3-monooxygenase (HbpA) locate activity hotspots identified by using directed evolution. Chembiochem 2015; 16:968-76. [PMID: 25737306 PMCID: PMC4515095 DOI: 10.1002/cbic.201402701] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Indexed: 11/09/2022]
Abstract
The FAD-dependent monooxygenase HbpA from Pseudomonas azelaica HBP1 catalyses the hydroxylation of 2-hydroxybiphenyl (2HBP) to 2,3-dihydroxybiphenyl (23DHBP). HbpA has been used extensively as a model for studying flavoprotein hydroxylases under process conditions, and has also been subjected to directed-evolution experiments that altered its catalytic properties. The structure of HbpA has been determined in its apo and FAD-complex forms to resolutions of 2.76 and 2.03 Å, respectively. Comparisons of the HbpA structure with those of homologues, in conjunction with a model of the reaction product in the active site, reveal His48 as the most likely acid/base residue to be involved in the hydroxylation mechanism. Mutation of His48 to Ala resulted in an inactive enzyme. The structures of HbpA also provide evidence that mutants achieved by directed evolution that altered activity are comparatively remote from the substrate-binding site.
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Affiliation(s)
- Chantel N Jensen
- York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York, YO10 5DD (UK)
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9
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Friedrich T, Mielke T, Domogalla M, Hentschel M, Kraus K, Tieke B. Photoisomerizable and ThermoresponsiveN-isopropylacrylamide-Surfmer Copolymer Hydrogels Prepared upon Electrostatic Self-Assembly of an Azobenzene Bolaamphiphile. Macromol Rapid Commun 2013; 34:393-8. [DOI: 10.1002/marc.201200630] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Revised: 11/27/2012] [Indexed: 11/12/2022]
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10
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11
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Abstract
Plant diversity and niche complementarity had progressively stronger effects on ecosystem functioning during a 7-year experiment, with 16-species plots attaining 2.7 times greater biomass than monocultures. Diversity effects were neither transients nor explained solely by a few productive or unviable species. Rather, many higher-diversity plots outperformed the best monoculture. These results help resolve debate over biodiversity and ecosystem functioning, show effects at higher than expected diversity levels, and demonstrate, for these ecosystems, that even the best-chosen monocultures cannot achieve greater productivity or carbon stores than higher-diversity sites.
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Affiliation(s)
- D Tilman
- Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, MN 55108, USA.
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12
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Dickopf S, Mielke T, Heyn MP. Kinetics of the light-induced proton translocation associated with the pH-dependent formation of the metarhodopsin I/II equilibrium of bovine rhodopsin. Biochemistry 1998; 37:16888-97. [PMID: 9836581 DOI: 10.1021/bi981879m] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The kinetics of the formation of the metaII (MII) state of bovine rhodopsin was investigated by time-resolved electrical and absorption measurements with rod outer segment (ROS) fragments. Photoexcitation leads to proton transfer in the direction from the cytosolic to the intradiscal side of the membrane, probably from the Schiff base to the acceptor glutamate 113. Two components of comparable amplitude are required to describe the charge movement with exponential times of 1.1 (45%) and 3.0 ms (55%) (pH 7.8, 22 degreesC, 150 mM KCl). The corresponding activation energies are 86 and 123 kJ/mol, respectively (150 mM KCl). The time constants and amplitudes depend strongly on pH. Between pH 7.1 and 3.8 the kinetics becomes much faster, with the faster and slower components accelerating by factors of about 8 and 2, respectively. Complementary single-flash absorption experiments at 380 nm and 10 degreesC show that the formation of MII also occurs with two components with similar time constants and pH dependence. This suggests that both signals monitor the same molecular events. The pH dependence of the two apparent time constants and amplitudes of the optical data can be described well over the pH range 4-7.5 by two coupled equilibria between MI and two isochromic MII species MIIa and MIIb: MI MIIa(380) MIIb(380), with k0 proportional to the proton concentration. This model implies that deprotonation of the Schiff base and proton uptake are tightly coupled in ROS membranes. Models with k2 proportional to the proton concentration cannot describe the data. Photoreversal of MII by blue flashes (420 nm) leads to proton transfer in a direction opposite to that of the signal associated with MII formation. In this transition the Schiff base is reprotonated, most likely from glutamate 113. At pH 7.3, 150 mM KCl, 22 degreesC, this electrical charge reversal has an exponential time constant of about 30 ms and is about 10 times slower than the forward charge motion.
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Affiliation(s)
- S Dickopf
- Biophysics Group, Department of Physics, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany
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13
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Welsh RS, Vyska K, Dohmen W, Mielke T, Chakravorty R, Mukherjee AS. Functional aspect of a phosphopeptide derived from calf thymus nuclei and DNA. Indian J Exp Biol 1990; 28:301-7. [PMID: 2351414] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Phosphopeptides (PPs) isolated from highly purified calf thymus DNA (N-DNA) and extracted from calf thymus nuclei were fractionated, and the effect of one PP fraction on DNA replication has been examined. In the absence of inhibitors, the increasing PP concentration caused a linear decrease of 3H-thymidine uptake in L5178Y cells. If PP fraction was mildly hydrolysed with 1NHCl, the decrease in uptake was much steeper. The studies in which the inhibitors were used revealed that by the addition of the unhydrolysed PP fraction the inhibition of 3H-thymidine uptake by alpha-amanitin could be completely overcome, and that the inhibition by puromycin was reduced to 65-77% of the control. With puromycin, there was a gradual decrease of 3H-thymidine uptake with PP concentration above 3 mg/ml. The PPs gave an increase in incorporation of 3H-thymidine even after removal of alpha-amanitin and puromycin; thus, it is suggested that there is no direct interaction of either inhibitor with PP in the cell. Data on the utilization of 3H-cytidine for the synthesise of new DNA suggest that PP fraction might cause an acceleration of DNA replication.
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Affiliation(s)
- R S Welsh
- Institute of Medicine, Nuclear Research Center, Julich, FRG
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Fidorra J, Mielke T, Booz J, Feinendegen LE. Cellular and nuclear volume of human cells during the cell cycle. Radiat Environ Biophys 1981; 19:205-214. [PMID: 7267987 DOI: 10.1007/bf01324188] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The volumes of whole cells and nuclei of cultured human cells were studied at different times after synchronization of growth using the Coulter counter and scanning microphotometry. It was found that the increase in cell volume is compatible with both linear or exponential growth during the cell cycle. The growth of the nuclear volume is not correlated with the beginning of the DNA synthesis. The nuclear volume starts to increase already 6 hr prior DNA synthesis. The data also indicate that the nuclear volume growth could proceed in two stages. The relation of this result to radiation sensitivity is discussed.
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