1
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Liu F, Zhang J. Nano-second protein dynamics of key residue at Position 38 in catechol-O-methyltransferase system: a time-resolved fluorescence study. J Biochem 2020; 168:417-425. [DOI: 10.1093/jb/mvaa063] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2020] [Accepted: 05/17/2020] [Indexed: 02/02/2023] Open
Abstract
AbstractHuman catechol-O-methyltransferase, a key enzyme related to neurotransmitter metabolism, catalyses a methyl transfer from S-adenosylmethionine to catechol. Although extensive studies aim to understand the enzyme mechanisms, the connection of protein dynamics and enzyme catalysis is still not clear. Here, W38in (Trp143Phe) and W38in/Y68A (Trp143Phe with Tyr68Ala) mutants were carried out to study the relationship of dynamics and catalysis in nano-second timescale using time-resolved fluorescence lifetimes and Stokes shifts in various solvents. The comprehensive data implied the mutant W38in/Y68A with lower activity is more rigid than the ‘WT’−W38in, suggesting the importance of flexibility at residue 38 to maintain the optimal catalysis.
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Affiliation(s)
- Fan Liu
- School of Pharmaceutical Science and Technology, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China
| | - Jianyu Zhang
- School of Pharmaceutical Science and Technology, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072, China
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2
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Roca M, Williams IH. Transition-State Vibrational Analysis and Isotope Effects for COMT-Catalyzed Methyl Transfer. J Am Chem Soc 2020; 142:15548-15559. [PMID: 32812761 PMCID: PMC7498148 DOI: 10.1021/jacs.0c07344] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Isotopic partition-function ratios (IPFRs) computed for transition structures (TSs) of the methyl-transfer reaction catalyzed by catechol O-methyltransferase and modeled by hybrid QM/MM methods are analyzed. The ability of smaller Hessians to reproduce trends in α-3H3 and 14Cα IPFRs as obtained using the much larger subset QM/MM Hessians from which they are extracted is investigated critically. A 6-atom-extracted Hessian reproduces perfectly the α-T3 IPFR values from the full-subset Hessians of all the TSs but not the α-14CIPFRs. Average AM1/OPLS-AA harmonic frequencies and mean-square amplitudes are presented for the 12 normal modes of the α-CH3 moiety within the active site of several enzymic transition structures, together with QM/MM potential energy scans along each of these modes to assess the degree of anharmonicity. A novel investigation of ponderal effects upon IPFRs suggests that the value for α-14C tends toward a limiting minimum whereas that for α-T3 tends toward a limiting maximum as the mass of the rest of the system increases. The transition vector is dominated by motions of atoms within the donor and acceptor moieties and is very well described as a simple combination of Walden-inversion "umbrella" bending and asymmetric stretching of the SCα and CαO bonds. The contribution of atoms of the protein residues Met40, Tyr68, and Asp141 to the transition vector is extremely small. Average valence force constants for the COMT TS show significant differences from early BEBOVIB estimates which were used in support of the compression hypothesis for catalysis. There is no correlation between TS IPFRs and the nonbonded distances for close contacts between the S atom of SAM and Tyr68 or between any of the H atoms of the transferring methyl group and either Met40 or Asp141.
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Affiliation(s)
- Maite Roca
- Departament de Química Física i Analítica, Universitat Jaume I, 12071 Castellón, Spain
| | - Ian H Williams
- Department of Chemistry, University of Bath, Bath BA2 7AY, United Kingdom
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3
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Zhang J, Balsbaugh JL, Gao S, Ahn NG, Klinman JP. Hydrogen deuterium exchange defines catalytically linked regions of protein flexibility in the catechol O-methyltransferase reaction. Proc Natl Acad Sci U S A 2020; 117:10797-10805. [PMID: 32371482 PMCID: PMC7245127 DOI: 10.1073/pnas.1917219117] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Human catechol O-methyltransferase (COMT) has emerged as a model for understanding enzyme-catalyzed methyl transfer from S-adenosylmethionine (AdoMet) to small-molecule catecholate acceptors. Mutation of a single residue (tyrosine 68) behind the methyl-bearing sulfonium of AdoMet was previously shown to impair COMT activity by interfering with methyl donor-acceptor compaction within the activated ground state of the wild type enzyme [J. Zhang, H. J. Kulik, T. J. Martinez, J. P. Klinman, Proc. Natl. Acad. Sci. U.S.A. 112, 7954-7959 (2015)]. This predicts the involvement of spatially defined protein dynamical effects that further tune the donor/acceptor distance and geometry as well as the electrostatics of the reactants. Here, we present a hydrogen/deuterium exchange (HDX)-mass spectrometric study of wild type and mutant COMT, comparing temperature dependences of HDX against corresponding kinetic and cofactor binding parameters. The data show that the impaired Tyr68Ala mutant displays similar breaks in Arrhenius plots of both kinetic and HDX properties that are absent in the wild type enzyme. The spatial resolution of HDX below a break point of 15-20 °C indicates changes in flexibility across ∼40% of the protein structure that is confined primarily to the periphery of the AdoMet binding site. Above 20 °C, Tyr68Ala behaves more like WT in HDX, but its rate and enthalpic barrier remain significantly altered. The impairment of catalysis by Tyr68Ala can be understood in the context of a mutationally induced alteration in protein motions that becomes manifest along and perpendicular to the primary group transfer coordinate.
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Affiliation(s)
- Jianyu Zhang
- Department of Chemistry, University of California, Berkeley, CA 94720
- The California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720
| | - Jeremy L Balsbaugh
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO 80309
- BioFrontiers Institute, University of Colorado Boulder, Boulder, CO 80309
| | - Shuaihua Gao
- Department of Chemistry, University of California, Berkeley, CA 94720
- The California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720
| | - Natalie G Ahn
- Department of Biochemistry, University of Colorado Boulder, Boulder, CO 80309;
- BioFrontiers Institute, University of Colorado Boulder, Boulder, CO 80309
| | - Judith P Klinman
- Department of Chemistry, University of California, Berkeley, CA 94720;
- The California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720
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4
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Świderek K, Porter AJ, Upfold CM, Williams IH. Influence of Dielectric Environment upon Isotope Effects on Glycoside Heterolysis: Computational Evaluation and Atomic Hessian Analysis. J Am Chem Soc 2020; 142:1556-1563. [PMID: 31887034 DOI: 10.1021/jacs.9b11988] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Isotope effects depend upon the polarity of the bulk medium in which a chemical process occurs. Implicit solvent calculations with molecule-shaped cavities show that the equilibrium isotope effect (EIE) for heterolysis of the glycosidic bonds in 5'-methylthioadenosine and in 2-(p-nitrophenoxy)tetrahydropyran, both in water, are very sensitive in the range 2 ≤ ε ≤ 10 to the relative permittivity of the continuum surrounding the oxacarbenium ion. However, different implementations of nominally the same PCM method can lead to opposite trends being predicted for the same molecule. Computational modeling of the influence of the inhomogeneous effective dielectric surrounding a substrate within the protein environment of an enzymic reaction requires an explicit treatment. The EIE (KH/KD) for transfer of cyclopentyl, cyclohexyl, tetrahydrofuranyl and tetrahydropyranyl cations from water to cyclohexane is predicted by B3LYP/6-31+G(d) calculations with implicit solvation and confirmed by B3LYP/6-31+G(d)/OPLS-AA calculations with averaging over many explicit solvation configurations. Atomic Hessian analysis, whereby the full Hessian is reduced to the elements belonging to a single atom at the site of isotopic substitution, reveals a remarkable result for both implicit and explicit solvation: the influence of the solvent environment on these EIEs is essentially captured completely by only a 3 × 3 block of the Hessian, although these values must correctly reflect the influence of the whole environment. QM/MM simulation with ensemble averaging has an important role to play in assisting the meaningful interpretation of observed isotope effects for chemical reactions both in solution and catalyzed by enzymes.
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Affiliation(s)
- Katarzyna Świderek
- Departament de Química Física i Analítica , Universitat Jaume I , 12071 Castellón , Spain.,Department of Chemistry , University of Bath , Bath BA2 7AY , United Kingdom
| | - Alexander J Porter
- Department of Chemistry , University of Bath , Bath BA2 7AY , United Kingdom
| | - Catherine M Upfold
- Department of Chemistry , University of Bath , Bath BA2 7AY , United Kingdom
| | - Ian H Williams
- Department of Chemistry , University of Bath , Bath BA2 7AY , United Kingdom
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5
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Glancy JH, Lee DM, Read EO, Williams IH. Computational simulation of mechanism and isotope effects on acetal heterolysis as a model for glycoside hydrolysis. PURE APPL CHEM 2019. [DOI: 10.1515/pac-2019-0221] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Abstract
DFT calculations for the equilibrium isotope effect for deuterium substitution at the anomeric centre Cα in 2-(p-nitrophenoxy)tetrahydropyran with continuum solvation show significant variation in the range of relative permittivity 2 ≤ ε ≤ 10. One-dimensional scans of potential energy (with implicit solvation by water) or of free energy (from QM/MM potentials of mean force with explicit aqueous solvation with a hybrid AM1/OPLS method) for heterolysis of the bond between Cα and the nucleofuge do not show a transition state. A two-dimensional free-energy surface that considers also the distance between Cα and a nucleophilic water indicates a pre-association DN*ANint
‡ mechanism with a transition state involving nucleophilic attack upon an ion-pair intermediate, and this is supported by good agreement between the mean values of the calculated and experimental α-D KIEs. However, the magnitudes of the standard deviations about the mean values for the making and breaking C–O bonds suggest that the transition state is rather plastic, with Cα–Onu≈2 ± 0.4 Å and Cα–Olg≈3 ± 0.5 Å. Not only is nucleophilic solvent assistance necessary, but there is also evidence for electrophilic assistance through specific hydrogen bonding to the nucleofuge.
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Affiliation(s)
- John H. Glancy
- Department of Chemistry , University of Bath , Bath BA2 7AY , UK
| | - Daniel M. Lee
- Department of Chemistry , University of Bath , Bath BA2 7AY , UK
| | - Emily O. Read
- Department of Chemistry , University of Bath , Bath BA2 7AY , UK
| | - Ian H. Williams
- Department of Chemistry , University of Bath , Bath BA2 7AY , UK
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6
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Czarnota S, Johannissen LO, Baxter NJ, Rummel F, Wilson AL, Cliff MJ, Levy CW, Scrutton NS, Waltho JP, Hay S. Equatorial Active Site Compaction and Electrostatic Reorganization in Catechol- O-methyltransferase. ACS Catal 2019; 9:4394-4401. [PMID: 31080692 PMCID: PMC6503465 DOI: 10.1021/acscatal.9b00174] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Revised: 03/26/2019] [Indexed: 12/18/2022]
Abstract
Catechol-O-methyltransferase (COMT) is a model S-adenosyl-l-methionine (SAM) dependent methyl transferase, which catalyzes the methylation of catecholamine neurotransmitters such as dopamine in the primary pathway of neurotransmitter deactivation in animals. Despite extensive study, there is no consensus view of the physical basis of catalysis in COMT. Further progress requires experimental data that directly probes active site geometry, protein dynamics and electrostatics, ideally in a range of positions along the reaction coordinate. Here we establish that sinefungin, a fungal-derived inhibitor of SAM-dependent enzymes that possess transition state-like charge on the transferring group, can be used as a transition state analog of COMT when combined with a catechol. X-ray crystal structures and NMR backbone assignments of the ternary complexes of the soluble form of human COMT containing dinitrocatechol, Mg2+ and SAM or sinefungin were determined. Comparison and further analysis with the aid of density functional theory calculations and molecular dynamics simulations provides evidence for active site "compaction", which is driven by electrostatic stabilization between the transferring methyl group and "equatorial" active site residues that are orthogonal to the donor-acceptor (pseudo reaction) coordinate. We propose that upon catecholamine binding and subsequent proton transfer to Lys 144, the enzyme becomes geometrically preorganized, with little further movement along the donor-acceptor coordinate required for methyl transfer. Catalysis is then largely facilitated through stabilization of the developing charge on the transferring methyl group via "equatorial" H-bonding and electrostatic interactions orthogonal to the donor-acceptor coordinate.
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Affiliation(s)
- Sylwia Czarnota
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- School
of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Linus O. Johannissen
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
| | - Nicola J. Baxter
- Krebs
Institute for Biomolecular Research, Department of Molecular Biology
and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, United Kingdom
| | - Felix Rummel
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- School
of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Alex L. Wilson
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- School
of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Matthew J. Cliff
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
| | - Colin W. Levy
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
| | - Nigel S. Scrutton
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- School
of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Jonathan P. Waltho
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- School
of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
- Krebs
Institute for Biomolecular Research, Department of Molecular Biology
and Biotechnology, The University of Sheffield, Firth Court, Western Bank, Sheffield, S10 2TN, United Kingdom
| | - Sam Hay
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- School
of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
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7
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Saez DA, Zinovjev K, Tuñón I, Vöhringer-Martinez E. Catalytic Reaction Mechanism in Native and Mutant Catechol-O-methyltransferase from the Adaptive String Method and Mean Reaction Force Analysis. J Phys Chem B 2018; 122:8861-8871. [DOI: 10.1021/acs.jpcb.8b07339] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- David Adrian Saez
- Departamento de Físico-Química, Facultad de Ciencias Químicas, Universidad de Concepción, 4070371 Concepcion, Chile
| | - Kirill Zinovjev
- Departament de Química Física, Universitat de València, 46100 Burjassot, Spain
| | - Iñaki Tuñón
- Departament de Química Física, Universitat de València, 46100 Burjassot, Spain
| | - Esteban Vöhringer-Martinez
- Departamento de Físico-Química, Facultad de Ciencias Químicas, Universidad de Concepción, 4070371 Concepcion, Chile
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8
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Abstract
Protein lysine methylation is a distinct posttranslational modification that causes minimal changes in the size and electrostatic status of lysine residues. Lysine methylation plays essential roles in regulating fates and functions of target proteins in an epigenetic manner. As a result, substrates and degrees (free versus mono/di/tri) of protein lysine methylation are orchestrated within cells by balanced activities of protein lysine methyltransferases (PKMTs) and demethylases (KDMs). Their dysregulation is often associated with neurological disorders, developmental abnormalities, or cancer. Methyllysine-containing proteins can be recognized by downstream effector proteins, which contain methyllysine reader domains, to relay their biological functions. While numerous efforts have been made to annotate biological roles of protein lysine methylation, limited work has been done to uncover mechanisms associated with this modification at a molecular or atomic level. Given distinct biophysical and biochemical properties of methyllysine, this review will focus on chemical and biochemical aspects in addition, recognition, and removal of this posttranslational mark. Chemical and biophysical methods to profile PKMT substrates will be discussed along with classification of PKMT inhibitors for accurate perturbation of methyltransferase activities. Semisynthesis of methyllysine-containing proteins will also be covered given the critical need for these reagents to unambiguously define functional roles of protein lysine methylation.
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Affiliation(s)
- Minkui Luo
- Chemical Biology Program , Memorial Sloan Kettering Cancer Center , New York , New York 10065 , United States.,Program of Pharmacology, Weill Graduate School of Medical Science , Cornell University , New York , New York 10021 , United States
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9
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Wilson PB. Recent advances in avian egg science: A review. Poult Sci 2018; 96:3747-3754. [PMID: 28938769 PMCID: PMC5850298 DOI: 10.3382/ps/pex187] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 06/13/2017] [Indexed: 12/21/2022] Open
Abstract
Eggs and egg products form an integral part of the food chain. As such, research into egg structure, function, and production has made an important contribution to the field of poultry science. The past decade has seen significant advances in avian egg science research, with work supplementing our understanding of the nature of the avian egg, and its biological, chemical, and physical properties. Eggshell color, strength, and chemical composition, poultry nutrition, and genetics have all been intensively studied recently, with significant progress being made in a number of these areas. Indeed, with the prevalence of robust theoretical techniques, it is now commonplace to combine experimental investigations with theory, providing a balanced and interdisciplinary perspective.
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Affiliation(s)
- Philippe B Wilson
- Faculty of Health & Life Sciences, De Montfort University, The Gateway, Leicester, LE1 9BH, United Kingdom
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10
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Wilson PB, Williams IH. Computational Modeling of a Caged Methyl Cation: Structure, Energetics, and Vibrational Analysis. J Phys Chem A 2018; 122:1432-1438. [DOI: 10.1021/acs.jpca.7b11836] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Philippe B. Wilson
- Department
of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom
- Leicester
School of Pharmacy, De Montfort University, The Gateway, Leicester LE1 9BH, United Kingdom
| | - Ian H. Williams
- Department
of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom
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11
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Ji L, Wang C, Ji S, Kepp KP, Paneth P. Mechanism of Cobalamin-Mediated Reductive Dehalogenation of Chloroethylenes. ACS Catal 2017. [DOI: 10.1021/acscatal.7b00540] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Li Ji
- College
of Environmental and Resource Sciences, Zhejiang University, Yuhangtang Road 866, Hangzhou 310058, China
| | - Chenchen Wang
- College
of Environmental and Resource Sciences, Zhejiang University, Yuhangtang Road 866, Hangzhou 310058, China
| | - Shujing Ji
- College
of Environmental and Resource Sciences, Zhejiang University, Yuhangtang Road 866, Hangzhou 310058, China
| | - Kasper P. Kepp
- DTU
Chemistry, Technical University of Denmark, Building 206, Kgs. Lyngby DK-2800, Denmark
| | - Piotr Paneth
- Institute
of Applied Radiation Chemistry, Faculty of Chemistry, Lodz University of Technology, Zeromskiego 116, 90-924 Lodz, Poland
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12
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Stratton CF, Poulin MB, Du Q, Schramm VL. Kinetic Isotope Effects and Transition State Structure for Human Phenylethanolamine N-Methyltransferase. ACS Chem Biol 2017; 12:342-346. [PMID: 27997103 PMCID: PMC5553282 DOI: 10.1021/acschembio.6b00922] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phenylethanolamine N-methyltransferase (PNMT) catalyzes the S-adenosyl-l-methionine (SAM)-dependent conversion of norepinephrine to epinephrine. Epinephrine has been associated with critical processes in humans including the control of respiration and blood pressure. Additionally, PNMT activity has been suggested to play a role in hypertension and Alzheimer's disease. In the current study, labeled SAM substrates were used to measure primary methyl-14C and 36S and secondary methyl-3H, 5'-3H, and 5'-14C intrinsic kinetic isotope effects for human PNMT. The transition state of human PNMT was modeled by matching kinetic isotope effects predicted via quantum chemical calculations to intrinsic values. The model provides information on the geometry and electrostatics of the human PNMT transition state structure and indicates that human PNMT catalyzes the formation of epinephrine through an early SN2 transition state in which methyl transfer is rate-limiting.
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Affiliation(s)
- Christopher F. Stratton
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, United States
| | | | - Quan Du
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, United States
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13
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Linscott JA, Kapilashrami K, Wang Z, Senevirathne C, Bothwell IR, Blum G, Luo M. Kinetic isotope effects reveal early transition state of protein lysine methyltransferase SET8. Proc Natl Acad Sci U S A 2016; 113:E8369-E8378. [PMID: 27940912 PMCID: PMC5206543 DOI: 10.1073/pnas.1609032114] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Protein lysine methyltransferases (PKMTs) catalyze the methylation of protein substrates, and their dysregulation has been linked to many diseases, including cancer. Accumulated evidence suggests that the reaction path of PKMT-catalyzed methylation consists of the formation of a cofactor(cosubstrate)-PKMT-substrate complex, lysine deprotonation through dynamic water channels, and a nucleophilic substitution (SN2) transition state for transmethylation. However, the molecular characters of the proposed process remain to be elucidated experimentally. Here we developed a matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) method and corresponding mathematic matrix to determine precisely the ratios of isotopically methylated peptides. This approach may be generally applicable for examining the kinetic isotope effects (KIEs) of posttranslational modifying enzymes. Protein lysine methyltransferase SET8 is the sole PKMT to monomethylate histone 4 lysine 20 (H4K20) and its function has been implicated in normal cell cycle progression and cancer metastasis. We therefore implemented the MS-based method to measure KIEs and binding isotope effects (BIEs) of the cofactor S-adenosyl-l-methionine (SAM) for SET8-catalyzed H4K20 monomethylation. A primary intrinsic 13C KIE of 1.04, an inverse intrinsic α-secondary CD3 KIE of 0.90, and a small but statistically significant inverse CD3 BIE of 0.96, in combination with computational modeling, revealed that SET8-catalyzed methylation proceeds through an early, asymmetrical SN2 transition state with the C-N and C-S distances of 2.35-2.40 Å and 2.00-2.05 Å, respectively. This transition state is further supported by the KIEs, BIEs, and steady-state kinetics with the SAM analog Se-adenosyl-l-selenomethionine (SeAM) as a cofactor surrogate. The distinct transition states between protein methyltransferases present the opportunity to design selective transition-state analog inhibitors.
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Affiliation(s)
- Joshua A Linscott
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065
- Program of Pharmacology, Weill Graduate School of Medical Science, Cornell University, New York, NY 10021
| | - Kanishk Kapilashrami
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| | - Zhen Wang
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Chamara Senevirathne
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| | - Ian R Bothwell
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| | - Gil Blum
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065
- Tri-Institutional PhD Program in Chemical Biology, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| | - Minkui Luo
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, New York, NY 10065;
- Program of Pharmacology, Weill Graduate School of Medical Science, Cornell University, New York, NY 10021
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14
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Zhang J, Klinman JP. Convergent Mechanistic Features between the Structurally Diverse N- and O-Methyltransferases: Glycine N-Methyltransferase and Catechol O-Methyltransferase. J Am Chem Soc 2016; 138:9158-65. [PMID: 27355841 PMCID: PMC5270642 DOI: 10.1021/jacs.6b03462] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
![]()
Although an enormous and still growing
number of biologically diverse
methyltransferases have been reported and identified, a comprehensive
understanding of the enzymatic methyl transfer mechanism is still
lacking. Glycine N-methyltransferase (GNMT), a member
of the family that acts on small metabolites as the substrate, catalyzes
methyl transfer from S-adenosyl-l-methionine
(AdoMet) to glycine to form S-adenosyl-l-homocysteine and sarcosine. We report primary carbon (12C/14C) and secondary (1H3/3H3) kinetic isotope effects at the transferred methyl
group, together with 1H3/3H3 binding isotope effects for wild-type GNMT and a series of Tyr21
mutants. The data implicate a compaction effect in the methyl transfer
step that is conferred by the protein structure. Furthermore, a remarkable
similarity of properties is observed between GNMT and catechol O-methyltransferase, despite significant differences between
these enzymes with regard to their active site structures and catalyzed
reactions. We attribute these results to a catalytically relevant
reduction in the methyl donor–acceptor distance that is dependent
on a tyrosine side chain positioned behind the methyl-bearing sulfur
of AdoMet.
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Affiliation(s)
- Jianyu Zhang
- Department of Chemistry, ‡Department of Molecular and Cell Biology, and §California Institute for Quantitative Biosciences, University of California , Berkeley, California 94720, United States
| | - Judith P Klinman
- Department of Chemistry, ‡Department of Molecular and Cell Biology, and §California Institute for Quantitative Biosciences, University of California , Berkeley, California 94720, United States
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