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Abstract
The disaccharide trehalose is accumulated in the cytoplasm of some organisms in response to harsh environmental conditions. Trehalose biosynthesis and accumulation are important for the survival of such organisms by protecting the structure and function of proteins and membranes. Trehalose affects the dynamics of proteins and water molecules in the bulk and the protein hydration shell. Enzyme catalysis and other processes dependent on protein dynamics are affected by the viscosity generated by trehalose, as described by the Kramers’ theory of rate reactions. Enzyme/protein stabilization by trehalose against thermal inactivation/unfolding is also explained by the viscosity mediated hindering of the thermally generated structural dynamics, as described by Kramers’ theory. The analysis of the relationship of viscosity–protein dynamics, and its effects on enzyme/protein function and other processes (thermal inactivation and unfolding/folding), is the focus of the present work regarding the disaccharide trehalose as the viscosity generating solute. Finally, trehalose is widely used (alone or in combination with other compounds) in the stabilization of enzymes in the laboratory and in biotechnological applications; hence, considering the effect of viscosity on catalysis and stability of enzymes may help to improve the results of trehalose in its diverse uses/applications.
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2
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Scharlau M, Geren L, Zhen EY, Ma L, Rajagukguk R, Ferguson-Miller S, Durham B, Millett F. Definition of the Interaction Domain and Electron Transfer Route between Cytochrome c and Cytochrome Oxidase. Biochemistry 2019; 58:4125-4135. [PMID: 31532642 DOI: 10.1021/acs.biochem.9b00646] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The reaction between cytochrome c (Cc) and cytochrome c oxidase (CcO) was studied using horse cytochrome c derivatives labeled with ruthenium trisbipyridine at Cys 39 (Ru-39-Cc). Flash photolysis of a 1:1 complex between Ru-39-Cc and bovine CcO at a low ionic strength resulted in the electron transfer from photoreduced heme c to CuA with an intracomplex rate constant of k3 = 6 × 104 s-1. The K13A, K72A, K86A, and K87A Ru-39-Cc mutants had nearly the same k3 value but bound much more weakly to bovine CcO than wild-type Ru-39-Cc, indicating that lysines 13, 72, 86, and 87 were involved in electrostatic binding to CcO, but were not involved in the electron transfer pathway. The Rhodobacter sphaeroides (Rs) W143F mutant (bovine W104) caused a 450-fold decrease in k3 but did not affect the binding strength with CcO or the redox potential of CuA. These results are consistent with a computational model for Cc-CcO (Roberts and Pique ( 1999 ) J. Biol. Chem. 274 , 38051 - 38060 ) with the following electron transfer pathway: heme c → CcO-W104 → CcO-M207 → CuA. A crystal structure for the Cc-CcO complex with the proposed electron transfer pathway heme c → Cc-C14 → Cc-K13 → CcO-Y105 → CcO-M207 → CuA ( S. Shimada ( 2017 ) EMBO J. 36 , 291 - 300 ) is not consistent with the kinetic results because the K13A mutation had no effect on k3. Addition of 40% ethylene glycol (as present during the crystal preparation) decreased k3 significantly, indicating that it affected the conformation of the complex. This may explain the discrepancy between the current results and the crystallographic structure.
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Affiliation(s)
- Martha Scharlau
- Department of Chemistry and Biochemistry , University of Arkansas , Fayetteville , Arkansas 72701 , United States
| | - Lois Geren
- Department of Chemistry and Biochemistry , University of Arkansas , Fayetteville , Arkansas 72701 , United States
| | - Eugene Y Zhen
- Department of Biochemistry and Molecular Biology , Michigan State University , East Lansing , Michigan 48824 , United States
| | - Ling Ma
- Department of Chemistry and Biochemistry , University of Arkansas , Fayetteville , Arkansas 72701 , United States
| | - Ray Rajagukguk
- Department of Chemistry and Biochemistry , University of Arkansas , Fayetteville , Arkansas 72701 , United States
| | - Shelagh Ferguson-Miller
- Department of Biochemistry and Molecular Biology , Michigan State University , East Lansing , Michigan 48824 , United States
| | - Bill Durham
- Department of Chemistry and Biochemistry , University of Arkansas , Fayetteville , Arkansas 72701 , United States
| | - Francis Millett
- Department of Chemistry and Biochemistry , University of Arkansas , Fayetteville , Arkansas 72701 , United States
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3
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Hedison TM, Heyes DJ, Shanmugam M, Iorgu AI, Scrutton NS. Solvent-slaved protein motions accompany proton coupled electron transfer reactions catalysed by copper nitrite reductase. Chem Commun (Camb) 2019; 55:5863-5866. [DOI: 10.1039/c9cc01026b] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A novel approach to study PCET reactions illustrates the importance of solvent-slaved protein motions in copper nitrite reductase catalysis.
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Affiliation(s)
- Tobias M. Hedison
- The Manchester Institute of Biotechnology
- University of Manchester
- Manchester
- UK
| | - Derren J. Heyes
- The Manchester Institute of Biotechnology
- University of Manchester
- Manchester
- UK
| | | | - Andreea I. Iorgu
- The Manchester Institute of Biotechnology
- University of Manchester
- Manchester
- UK
| | - Nigel S. Scrutton
- The Manchester Institute of Biotechnology
- University of Manchester
- Manchester
- UK
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4
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Corral Arroyo P, Bartels-Rausch T, Alpert PA, Dumas S, Perrier S, George C, Ammann M. Particle-Phase Photosensitized Radical Production and Aerosol Aging. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:7680-7688. [PMID: 29898357 DOI: 10.1021/acs.est.8b00329] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Atmospheric aerosol particles may contain light absorbing (brown carbon, BrC), triplet forming organic compounds that can sustain catalytic radical reactions and thus contribute to oxidative aerosol aging. We quantify UVA induced radical production initiated by imidazole-2-carboxaldehyde (IC), benzophenone (BPh). and 4-benzoylbenzoic acid (BBA) in the presence of the nonabsorbing organics citric acid (CA), shikimic acid (SA), and syringol (Syr) at varying mixing ratios. We observed a maximum HO2 release of 1013 molecules min-1 cm-2 at a mole ratio XBPh < 0.02 for BPh in CA. Mixtures of either IC or BBA with CA resulted in 1011-1012 molecules min-1 cm-2 of HO2 at mole ratios ( XIC and XBBA) between 0.01 and 0.15. HO2 release was affected by relative humidity ( RH) and film thickness suggesting coupled photochemical reaction and diffusion processes. Quantum yields of HO2 formed per absorbed photon for IC, BBA and BPh were between 10-7 and 5 × 10-5. The nonphotoactive organics, Syr and SA, increased HO2 production due to the reaction with the triplet excited species ensuing ketyl radical production. Rate coefficients of the triplet of IC with Syr and SA measured by laser flash photolysis experiments were kSyr = (9.4 ± 0.3) × 108 M-1 s-1 and kSA = (2.7 ± 0.5) × 107 M-1 s-1. A simple kinetic model was used to assess total HO2 and organic radical production in the condensed phase and to upscale to ambient aerosol, indicating that BrC induced radical production may amount to an upper limit of 20 and 200 M day-1 of HO2 and organic radical respectively, which is greater or in the same order of magnitude as the internal radical production from other processes, previously estimated to be around 15 M per day.
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Affiliation(s)
- Pablo Corral Arroyo
- Paul Scherrer Institute , Laboratory of Environmental Chemistry , 5232 Villigen PSI , Switzerland
- Department of Chemistry and Biochemistry , University of Bern , 2012 Bern , Switzerland
| | - Thorsten Bartels-Rausch
- Paul Scherrer Institute , Laboratory of Environmental Chemistry , 5232 Villigen PSI , Switzerland
| | - Peter A Alpert
- Paul Scherrer Institute , Laboratory of Environmental Chemistry , 5232 Villigen PSI , Switzerland
| | - Stéphane Dumas
- CNRS, UMR5256, IRCELYON , Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, IRCELYON , F-69626 , Villeurbanne , France
| | - Sébastien Perrier
- CNRS, UMR5256, IRCELYON , Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, IRCELYON , F-69626 , Villeurbanne , France
| | - Christian George
- CNRS, UMR5256, IRCELYON , Univ. Lyon, Université Claude Bernard Lyon 1, CNRS, IRCELYON , F-69626 , Villeurbanne , France
| | - Markus Ammann
- Paul Scherrer Institute , Laboratory of Environmental Chemistry , 5232 Villigen PSI , Switzerland
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5
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Jones HBL, Wells SA, Prentice EJ, Kwok A, Liang LL, Arcus VL, Pudney CR. A complete thermodynamic analysis of enzyme turnover links the free energy landscape to enzyme catalysis. FEBS J 2017. [PMID: 28650586 DOI: 10.1111/febs.14152] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Our understanding of how enzymes work is coloured by static structure depictions where the enzyme scaffold is presented as either immobile, or in equilibrium between well-defined static conformations. Proteins, however, exhibit a large degree of motion over a broad range of timescales and magnitudes and this is defined thermodynamically by the enzyme free energy landscape (FEL). The role and importance of enzyme motion is extremely contentious. Much of the challenge is in the experimental detection of so called 'conformational sampling' involved in enzyme turnover. Herein we apply combined pressure and temperature kinetics studies to elucidate the full suite of thermodynamic parameters defining an enzyme FEL as it relates to enzyme turnover. We find that the key thermodynamic parameters governing vibrational modes related to enzyme turnover are the isobaric expansivity term and the change in heat capacity for enzyme catalysis. Variation in the enzyme FEL affects these terms. Our analysis is supported by a range of biophysical and computational approaches that specifically capture information on protein vibrational modes and the FEL (all atom flexibility calculations, red edge excitation shift spectroscopy and viscosity studies) that provide independent evidence for our findings. Our data suggest that restricting the enzyme FEL may be a powerful strategy when attempting to rationally engineer enzymes, particularly to alter thermal activity. Moreover, we demonstrate how rational predictions can be made with a rapid computational approach.
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Affiliation(s)
- Hannah B L Jones
- Department of Biology and Biochemistry, Faculty of Science, University of Bath, UK
| | - Stephen A Wells
- Department of Chemical Engineering, Faculty of Science, University of Bath, UK
| | - Erica J Prentice
- School of Science, Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
| | - Anthony Kwok
- Department of Biology and Biochemistry, Faculty of Science, University of Bath, UK
| | - Liyin L Liang
- School of Science, Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
| | - Vickery L Arcus
- School of Science, Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
| | - Christopher R Pudney
- Department of Biology and Biochemistry, Faculty of Science, University of Bath, UK
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6
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Trana EN, Nocek JM, Woude JV, Span I, Smith SM, Rosenzweig AC, Hoffman BM. Charge-Disproportionation Symmetry Breaking Creates a Heterodimeric Myoglobin Complex with Enhanced Affinity and Rapid Intracomplex Electron Transfer. J Am Chem Soc 2016; 138:12615-28. [PMID: 27646786 DOI: 10.1021/jacs.6b07672] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
We report rapid photoinitiated intracomplex electron transfer (ET) within a "charge-disproportionated" myoglobin (Mb) dimer with greatly enhanced affinity. Two mutually supportive Brownian Dynamics (BD) interface redesign strategies, one a new "heme-filtering" approach, were employed to "break the symmetry" of a Mb homodimer by pairing Mb constructs with complementary highly positive and highly negative net surface charges, introduced through D/E → K and K → E mutations, respectively. BD simulations using a previously developed positive mutant, Mb(+6) = Mb(D44K/D60K/E85K), led to construction of the complementary negative mutant Mb(-6) = Mb(K45E, K63E, K95E). Simulations predict the pair will form a well-defined complex comprising a tight ensemble of conformations with nearly parallel hemes, at a metal-metal distance ∼18-19 Å. Upon expression and X-ray characterization of the partners, BD predictions were verified through ET photocycle measurements enabled by Zn-deuteroporphyrin substitution, forming the [ZnMb(-6), Fe(3+)Mb(+6)] complex. Triplet ET quenching shows charge disproportionation increases the binding constant by no less than ∼5 orders of magnitude relative to wild-type Mb values. All progress curves for charge separation (CS) and charge recombination (CR) are reproduced by a generalized kinetic model for the interprotein ET photocycle. The intracomplex ET rate constants for both CS and CR are increased by over 5 orders of magnitude, and their viscosity independence is indicative of true interprotein ET, rather than dynamic gating as seen in previous studies. The complex displays an unprecedented timecourse for CR of the CS intermediate I. After a laser flash, I forms through photoinduced CS, accumulates to a maximum concentration, then dies away through CR. However, before completely disappearing, I reappears without another flash and reaches a second maximum before disappearing completely.
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Affiliation(s)
- Ethan N Trana
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Judith M Nocek
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Jon Vander Woude
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
| | - Ingrid Span
- Department of Molecular Biosciences, Northwestern University , Evanston, Illinois 60208, United States
| | - Stephen M Smith
- Department of Molecular Biosciences, Northwestern University , Evanston, Illinois 60208, United States
| | - Amy C Rosenzweig
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.,Department of Molecular Biosciences, Northwestern University , Evanston, Illinois 60208, United States
| | - Brian M Hoffman
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.,Department of Molecular Biosciences, Northwestern University , Evanston, Illinois 60208, United States
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7
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Romero E, Ladani ST, Hamelberg D, Gadda G. Solvent-Slaved Motions in the Hydride Tunneling Reaction Catalyzed by Human Glycolate Oxidase. ACS Catal 2016. [DOI: 10.1021/acscatal.5b02889] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Elvira Romero
- Department of Chemistry, ¶Department of Biology, ∥Center for Biotechnology
and Drug
Design, and #Center
for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30302-3965, United States
| | - Safieh Tork Ladani
- Department of Chemistry, ¶Department of Biology, ∥Center for Biotechnology
and Drug
Design, and #Center
for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30302-3965, United States
| | - Donald Hamelberg
- Department of Chemistry, ¶Department of Biology, ∥Center for Biotechnology
and Drug
Design, and #Center
for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30302-3965, United States
| | - Giovanni Gadda
- Department of Chemistry, ¶Department of Biology, ∥Center for Biotechnology
and Drug
Design, and #Center
for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia 30302-3965, United States
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8
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Hoeven R, Hardman SJO, Heyes DJ, Scrutton NS. Cross-Species Analysis of Protein Dynamics Associated with Hydride and Proton Transfer in the Catalytic Cycle of the Light-Driven Enzyme Protochlorophyllide Oxidoreductase. Biochemistry 2016; 55:903-13. [DOI: 10.1021/acs.biochem.5b01355] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Robin Hoeven
- Centre for Synthetic Biology
of Fine and Speciality Chemicals, Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K
| | - Samantha J. O. Hardman
- Centre for Synthetic Biology
of Fine and Speciality Chemicals, Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K
| | - Derren J. Heyes
- Centre for Synthetic Biology
of Fine and Speciality Chemicals, Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K
| | - Nigel S. Scrutton
- Centre for Synthetic Biology
of Fine and Speciality Chemicals, Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K
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9
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Erratum: Internal friction in enzyme reactions, IUBMB life, 2012, Jan;65(1):35-42. IUBMB Life 2013. [DOI: 10.1002/iub.1225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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10
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Rauscher A, Derényi I, Gráf L, Málnási-Csizmadia A. Internal friction in enzyme reactions. IUBMB Life 2013; 65:35-42. [PMID: 23281036 DOI: 10.1002/iub.1101] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Accepted: 09/21/2012] [Indexed: 11/11/2022]
Abstract
The empirical concept of internal friction was introduced 20 years ago. This review summarizes the results of experimental and theoretical studies that help to uncover the nature of internal friction. After the history of the concept, we describe the experimental challenges in measuring and interpreting internal friction based on the viscosity dependence of enzyme reactions. We also present speculations about the structural background of this viscosity dependence. Finally, some models about the relationship between the energy landscape and internal friction are outlined. Alternative concepts regarding the viscosity dependence of enzyme reactions are also discussed.
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Affiliation(s)
- Anna Rauscher
- Department of Biochemistry, Eötvös University, Budapest, Hungary
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11
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Simultaneous true, gated, and coupled electron-transfer reactions and energetics of protein rearrangement. J Inorg Biochem 2012; 106:143-50. [DOI: 10.1016/j.jinorgbio.2011.09.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Revised: 09/06/2011] [Accepted: 09/09/2011] [Indexed: 11/19/2022]
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12
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Loveridge EJ, Tey LH, Behiry EM, Dawson WM, Evans RM, Whittaker SBM, Günther UL, Williams C, Crump MP, Allemann RK. The role of large-scale motions in catalysis by dihydrofolate reductase. J Am Chem Soc 2011; 133:20561-70. [PMID: 22060818 PMCID: PMC3590880 DOI: 10.1021/ja208844j] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Dihydrofolate reductase has long been used as a model system to study the coupling of protein motions to enzymatic hydride transfer. By studying environmental effects on hydride transfer in dihydrofolate reductase (DHFR) from the cold-adapted bacterium Moritella profunda (MpDHFR) and comparing the flexibility of this enzyme to that of DHFR from Escherichia coli (EcDHFR), we demonstrate that factors that affect large-scale (i.e., long-range, but not necessarily large amplitude) protein motions have no effect on the kinetic isotope effect on hydride transfer or its temperature dependence, although the rates of the catalyzed reaction are affected. Hydrogen/deuterium exchange studies by NMR-spectroscopy show that MpDHFR is a more flexible enzyme than EcDHFR. NMR experiments with EcDHFR in the presence of cosolvents suggest differences in the conformational ensemble of the enzyme. The fact that enzymes from different environmental niches and with different flexibilities display the same behavior of the kinetic isotope effect on hydride transfer strongly suggests that, while protein motions are important to generate the reaction ready conformation, an optimal conformation with the correct electrostatics and geometry for the reaction to occur, they do not influence the nature of the chemical step itself; large-scale motions do not couple directly to hydride transfer proper in DHFR.
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Affiliation(s)
- E Joel Loveridge
- School of Chemistry, Cardiff University, Park Place, Cardiff CF10 3AT, United Kingdom
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13
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Waldeck DH, Khoshtariya DE. Fundamental Studies of Long- and Short-Range Electron Exchange Mechanisms between Electrodes and Proteins. MODERN ASPECTS OF ELECTROCHEMISTRY 2011. [DOI: 10.1007/978-1-4614-0347-0_2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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14
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Jankowska KI, Pagba CV, Piatnitski Chekler EL, Deshayes K, Piotrowiak P. Electrostatic docking of a supramolecular host-guest assembly to cytochrome c probed by bidirectional photoinduced electron transfer. J Am Chem Soc 2010; 132:16423-31. [PMID: 21038913 DOI: 10.1021/ja102188e] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A water-soluble octacarboxyhemicarcerand was used as a shuttle to transport redox-active substrates across the aqueous medium and deliver them to the target protein. The results show that weak multivalent interactions and conformational flexibility can be exploited to reversibly bind complex supramolecular assemblies to biological molecules. Hydrophobic electron donors and acceptors were encapsulated within the hemicarcerand, and photoinduced electron transfer (ET) between the Zn-substituted cytochrome c (MW = 12.3 kD) and the host-guest complexes (MW = 2.2 kD) was used to probe the association between the negatively charged hemicarceplex and the positively charged protein. The behavior of the resulting ternary protein-hemicarcerand-guest assembly was investigated in two binding limits: (1) when K(encaps) ≫ K(assoc), the hemicarcerand transports the ligand to the protein while protecting it from the aqueous medium; and (2) when K(assoc) > K(encaps), the hemicarcerand-protein complex is formed first, and the hemicarcerand acts as an artificial receptor site that intercepts ligands from solution and positions them close to the active site of the metalloenzyme. In both cases, ET mediated by the protein-bound hemicarcerand is much faster than that due to diffusional encounters with the respective free donor or acceptor in solution. The measured ET rates suggest that the dominant binding region of the host-guest complex on the surface of the protein is consistent with the docking area of the native redox partner of cytochrome c. The strong association with the protein is attributed to the flexible conformation and adaptable charge distribution of the hemicarcerand, which allow for surface-matching with the cytochrome.
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Affiliation(s)
- Katarzyna I Jankowska
- Department of Chemistry, Rutgers University, 73 Warren Street, Newark, New Jersey 07102, United States
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15
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Loveridge EJ, Tey LH, Allemann RK. Solvent effects on catalysis by Escherichia coli dihydrofolate reductase. J Am Chem Soc 2010; 132:1137-43. [PMID: 20047317 DOI: 10.1021/ja909353c] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Hydride transfer catalyzed by dihydrofolate reductase (DHFR) has been described previously within an environmentally coupled model of hydrogen tunneling, where protein motions control binding of substrate and cofactor to generate a tunneling ready conformation and modulate the width of the activation barrier and hence the reaction rate. Changes to the composition of the reaction medium are known to perturb protein motions. We have measured kinetic parameters of the reaction catalyzed by DHFR from Escherichia coli in the presence of various cosolvents and cosolutes and show that the dielectric constant, but not the viscosity, of the reaction medium affects the rate of reaction. Neither the primary kinetic isotope effect on the reaction nor its temperature dependence were affected by changes to the bulk solvent properties. These results are in agreement with our previous report on the effect of solvent composition on catalysis by DHFR from the hyperthermophile Thermotoga maritima. However, the effect of solvent on the temperature dependence of the kinetic isotope effect on hydride transfer catalyzed by E. coli DHFR is difficult to explain within a model, in which long-range motions couple to the chemical step of the reaction, but may indicate the existence of a short-range promoting vibration or the presence of multiple nearly isoenergetic conformational substates of enzymes with similar but distinct catalytic properties.
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Affiliation(s)
- E Joel Loveridge
- School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, UK
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16
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Menon BRK, Davison PA, Hunter CN, Scrutton NS, Heyes DJ. Mutagenesis alters the catalytic mechanism of the light-driven enzyme protochlorophyllide oxidoreductase. J Biol Chem 2009; 285:2113-9. [PMID: 19850924 DOI: 10.1074/jbc.m109.071522] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The light-activated enzyme protochlorophyllide oxidoreductase (POR) catalyzes an essential step in the synthesis of the most abundant pigment on Earth, chlorophyll. This unique reaction involves the sequential addition of a hydride and proton across the C17=C18 double bond of protochlorophyllide (Pchlide) by dynamically coupled quantum tunneling and is an important model system for studying the mechanism of hydrogen transfer reactions. In the present work, we have combined site-directed mutagenesis studies with a variety of sensitive spectroscopic and kinetic measurements to provide new insights into the mechanistic role of three universally conserved Cys residues in POR. We show that mutation of Cys-226 dramatically alters the catalytic mechanism of the enzyme. In contrast to wild-type POR, the characteristic charge-transfer intermediate, formed upon hydride transfer from NADPH to the C17 position of Pchlide, is absent in C226S variant enzymes. This suggests a concerted hydrogen transfer mechanism where proton transfer only is rate-limiting. Moreover, Pchlide reduction does not require the network of solvent-coupled conformational changes that play a key role in the proton transfer step of wild-type POR. We conclude that this globally important enzyme is finely tuned to facilitate efficient photochemistry, and the removal of a key interaction with Pchlide in the C226S variants significantly affects the local active site structure in POR, resulting in a shorter donor-acceptor distance for proton transfer.
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Affiliation(s)
- Binuraj R K Menon
- Manchester Interdisciplinary Biocentre, Faculty of Life Sciences, University of Manchester, Manchester M17DN
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17
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Hay S, Pudney CR, Scrutton NS. Structural and mechanistic aspects of flavoproteins: probes of hydrogen tunnelling. FEBS J 2009; 276:3930-41. [DOI: 10.1111/j.1742-4658.2009.07121.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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18
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Heyes DJ, Sakuma M, Scrutton NS. Solvent-slaved protein motions accompany proton but not hydride tunneling in light-activated protochlorophyllide oxidoreductase. Angew Chem Int Ed Engl 2009; 48:3850-3. [PMID: 19373814 DOI: 10.1002/anie.200900086] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
H(+) but not H(-): The reduction reaction of protochlorophyllide catalyzed by protochlorophyllide oxidoreductase features solvent-slaved motions that control the proton- but not the hydride-tunneling mechanism. These motions imply a long-range dynamic network from the solvent to the enzyme active site that facilitate proton transfer (see picture, left). Motions for hydride transfer are more localized and are not slaved by the solvent (see picture, right).
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Affiliation(s)
- Derren J Heyes
- Manchester Interdisciplinary Biocentre, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester M1 7DN, UK.
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19
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Heyes D, Sakuma M, Scrutton N. Solvent-Slaved Protein Motions Accompany Proton but Not Hydride Tunneling in Light-Activated Protochlorophyllide Oxidoreductase. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200900086] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Hay S, Sutcliffe MJ, Scrutton NS. Probing Coupled Motions in Enzymatic Hydrogen Tunnelling Reactions: Beyond Temperature-Dependence Studies of Kinetic Isotope Effects. QUANTUM TUNNELLING IN ENZYME-CATALYSED REACTIONS 2009. [DOI: 10.1039/9781847559975-00199] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Sam Hay
- Faculty of Life Sciences, Manchester Interdisciplinary Biocentre, University of Manchester 131 Princess Street Manchester M1 7DN UK
| | - Michael J. Sutcliffe
- School of Chemical Engineering and Analytical Science, Manchester Interdisciplinary Biocentre, University of Manchester 131 Princess Street Manchester M1 7DN UK
| | - Nigel S. Scrutton
- Faculty of Life Sciences, Manchester Interdisciplinary Biocentre, University of Manchester 131 Princess Street Manchester M1 7DN UK
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Electron transfer from cytochrome c to cupredoxins. J Biol Inorg Chem 2009; 14:821-8. [DOI: 10.1007/s00775-009-0494-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2008] [Accepted: 02/28/2009] [Indexed: 10/21/2022]
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22
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Patel AD, Nocek JM, Hoffman BM. Kinetic-dynamic model for conformational control of an electron transfer photocycle: mixed-metal hemoglobin hybrids. J Phys Chem B 2008; 112:11827-37. [PMID: 18717535 PMCID: PMC2672620 DOI: 10.1021/jp8054679] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
It is becoming increasingly clear that the transfer of an electron across a protein-protein interface is coupled to the dynamics of conformational conversion between and within ensembles of interface conformations. Electron transfer (ET) reactions in conformationally mobile systems provide a "clock" against which the rapidity of a dynamic process may be measured, and we here report a simple kinetic (master equation) model that self-consistently incorporates conformational dynamics into an ET photocycle comprised of a photoinitiated "forward" step and thermal return to ground. This kinetic/dynamic (KD) model assumes an ET complex exists as multiple interconverting conformations which partition into an ET-optimized (reactive; R) population and a less-reactive population ( S). We take the members of each population to be equivalent by constraining them to have the same conformational energy, the same average rate constant for conversion to members of the other population, and the same rate constants for forward and back ET. The result is a mapping of a complicated energy surface onto the simple "gating", two-well surface, but with rate constants that are defined microscopically. This model successfully describes the changes in the ET photocycle within the "predocked" mixed-metal hemoglobin (Hb) hybrid, [alpha(Zn), beta(Fe3+N 3 (-))], as conformational kinetics are modulated by variations in viscosity (eta = 1-15 cP; 20 degrees C). The description reveals how the conformational "routes" by which a hybrid progresses through a photocycle differ in different dynamic regimes. Even at eta = 1 cP, the populations are not in fast exchange, and ET involves a complex interplay between conformational and ET processes; at intermediate viscosities the hybrid exhibits "differential dynamics" in which the forward and back ET processes involve different initial ensembles of configurational substates; by eta = 15 cP, the slow-exchange limit is approached. Even at low viscosity, the ET-coupled motions are fairly slow, with rate constants of <10 (3) s (-1). Current ideas about Hb function lead to the testable hypothesis that ET in the hybrid may be coupled to allosteric fluctuations of the two [alpha 1, beta 2] dimers of Hb.
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Affiliation(s)
- Ami D Patel
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
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Hay S, Pudney CR, Sutcliffe MJ, Scrutton NS. Are environmentally coupled enzymatic hydrogen tunneling reactions influenced by changes in solution viscosity? Angew Chem Int Ed Engl 2008; 47:537-40. [PMID: 18058788 DOI: 10.1002/anie.200704484] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Sam Hay
- Manchester Interdisciplinary Biocentre, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester M1 7DN, UK.
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Hay S, Pudney C, Sutcliffe M, Scrutton N. Are Environmentally Coupled Enzymatic Hydrogen Tunneling Reactions Influenced by Changes in Solution Viscosity? Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200704484] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Kuznetsov VY, Poulos TL, Sevrioukova IF. Putidaredoxin-to-cytochrome P450cam electron transfer: differences between the two reductive steps required for catalysis. Biochemistry 2006; 45:11934-44. [PMID: 17002293 PMCID: PMC2533851 DOI: 10.1021/bi0611154] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cytochrome P450cam (P450cam) is the terminal monooxygenase in a three-component camphor-hydroxylating system from Pseudomonas putida. The reaction cycle requires two distinct electron transfer (ET) processes from the [2Fe-2S] containing putidaredoxin (Pdx) to P450cam. Even though the mechanism of interaction and ET between the two proteins has been under investigation for over 30 years, the second reductive step and the effector role of Pdx are not fully understood. We utilized mutagenesis, kinetic, and computer modeling approaches to better understand differences between the two Pdx-to-P450cam ET events. Our results indicate that interacting residues and the ET pathways in the complexes formed between reduced Pdx (Pdx(r)) and the ferric and ferrous dioxygen-bound forms of P450cam (oxy-P450cam) are different. Pdx Asp38 and Trp106 were found to be key players in both reductive steps. Compared to the wild-type Pdx, the D38A, W106A, and delta106 mutants exhibited considerably higher Kd values for ferric P450cam and retained ca. 20% of the first electron transferring ability. In contrast, the binding affinity of the mutants for oxy-P450cam was not substantially altered while the second ET rates were <1%. On the basis of the kinetic and modeling data we conclude that (i) P450cam-Pdx interaction is highly specific in part because it is guided/controlled by the redox state of both partners; (ii) there are alternative ET routes from Pdx(r) to ferric P450cam and a unique pathway to oxy-P450cam involving Asp38; (iii) Pdx Trp106 is a key structural element that couples the second ET event to product formation possibly via its "push" effect on the heme-binding loop.
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Affiliation(s)
- Vadim Yu. Kuznetsov
- Departments of Molecular Biology and Biochemistry, University of California, Irvine, California 92697-3900
| | - Thomas L. Poulos
- Departments of Molecular Biology and Biochemistry, University of California, Irvine, California 92697-3900
- Departments of Physiology and Biophysics, University of California, Irvine, California 92697-3900
- Departments of Chemistry, University of California, Irvine, California 92697-3900
- Center in Chemical and Structural Biology, University of California, Irvine, California 92697-3900
| | - Irina F. Sevrioukova
- Departments of Molecular Biology and Biochemistry, University of California, Irvine, California 92697-3900
- To whom correspondence should be addressed: Tel: 949-824-1953, Fax: 949-824-3280, E-mail:
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Reduction of plastocyanin by tyrosine-containing oligopeptides. J Inorg Biochem 2006; 100:1871-8. [PMID: 16963123 DOI: 10.1016/j.jinorgbio.2006.07.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2006] [Revised: 06/09/2006] [Accepted: 07/23/2006] [Indexed: 11/22/2022]
Abstract
Oxidized plastocyanin (PC) was reduced with TyrTyrTyr and LysLysLysLysTyrTyrTyr (KKKKYYY) oligopeptides at neutral pH. The TyrTyrTyr site of the peptides provided an electron to the copper active site of PC, whereas the tetralysine site of KKKKYYY functioned as the recognition site for the negative patch of PC. The reciprocal initial rate constant (1/k(int)) increased linearly with the reciprocal TyrTyrTyr concentration and proton concentration, although the electron transfer rate decreased gradually with time. The results showed that PC was reduced by the deprotonated species of TyrTyrTyr. A linear increase of log k(int) with increase in the ionic strength was observed due to decrease in the electrostatic repulsion between negatively charged PC and deprotonated (TyrTyrTyr)(-). PC was reduced faster by an addition of KKKKYYY to the PC-TyrTyrTyr solution, although KKKKYYY could not reduce PC without TyrTyrTyr. The ESI-LCMS spectrum of the products from the reaction between PC and TyrTyrTyr showed molecular ion peaks at m/z 1015.7 and 1037.7, which suggested formation of a dimerized peptide that may be produced from the reaction of a tyrosyl radical. The results indicate that PC and the tyrosine-containing oligopeptides form an equilibrium, PC(ox)/(oligopeptide)(-)-->/<--PC(red)/(oligopeptide)(*). The equilibrium is usually shifted to the left, but could shift to the right when the produced oligopeptide radical reacts with unreacted peptides. For the reaction of PC with KKKKYYY in the absence of TyrTyrTyr, the produced KKKK(YYY)(*) radical peptide could not react with other KKKKYYY peptides, since they were positively charged. In the presence of both KKKKYYY and TyrTyrTyr, PC may interact effectively with KKKKYYY through its tetralysine site and receive an electron from its TyrTyrTyr site, where the produced KKKK(YYY)(*) may interact with TyrTyrTyr peptides.
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Szaciłowski K, Macyk W, Drzewiecka-Matuszek A, Brindell M, Stochel G. Bioinorganic photochemistry: frontiers and mechanisms. Chem Rev 2005; 105:2647-94. [PMID: 15941225 DOI: 10.1021/cr030707e] [Citation(s) in RCA: 561] [Impact Index Per Article: 29.5] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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28
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Hirota S, Okumura H, Kuroiwa S, Funasaki N, Watanabe Y. Reduction of ferricytochrome c by tyrosyltyrosylphenylalanine. J Biol Inorg Chem 2005; 10:355-63. [PMID: 15868183 DOI: 10.1007/s00775-005-0644-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2004] [Accepted: 03/30/2005] [Indexed: 10/25/2022]
Abstract
Cytochrome c (cyt c) was reduced by a tyrosine-containing peptide, tyrosyltyrosylphenylalanine (TyrTyrPhe), at pH 6.0-8.0, while tyrosinol or tyrosyltyrosine (TyrTyr) could not reduce cyt c effectively under the same condition. Cyt c was reduced at high peptide concentration, whereas the reaction did not occur effectively at low concentration. The reaction rate varied with time owing to a decrease in the TyrTyrPhe concentration and the production of tyrosine derivatives during the reaction. The initial rate constants were 2.4 x 10(-4) and 8.1 x 10(-4) s(-1) at pH 7.0 and 8.0, respectively, for the reaction with 1.0 mM TyrTyrPhe in 10 mM phosphate buffer at 15 degrees C. The reciprocal initial rate constant (1/k(int)) increased linearly against the reciprocal peptide concentration and against the linear proton concentration, whereas logk(int) decreased linearly against the root of the ionic strength. These results show that deprotonated (TyrTyrPhe)(-), presumably deprotonated at a tyrosine site, reduces cyt c by formation of an electrostatic complex. No significant difference in the reaction rate was observed between the reaction under nitrogen and oxygen atmospheres. From the matrix-assisted laser desorption ionization time-of-flight mass spectra of the reaction products, formation of a quinone and other tyrosine derivatives of the peptide was supported. These products should have been produced from a tyrosyl radical. We interpret the results that a cyt c(ox)/(TyrTyrPhe)(-)right harpoon over left harpooncyt c(red)/(TyrTyrPhe)(*) equilibrium is formed, which is usually shifted to the left. This equilibrium may shift to the right by reaction of the produced tyrosyl radical with the tyrosine sites of unreacted TyrTyrPhe peptides.
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Affiliation(s)
- S Hirota
- Department of Physical Chemistry, 21st Century COE Program, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, 607-8414 Kyoto, Japan.
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Hoffman BM, Celis LM, Cull DA, Patel AD, Seifert JL, Wheeler KE, Wang J, Yao J, Kurnikov IV, Nocek JM. Differential influence of dynamic processes on forward and reverse electron transfer across a protein-protein interface. Proc Natl Acad Sci U S A 2005; 102:3564-9. [PMID: 15738411 PMCID: PMC553314 DOI: 10.1073/pnas.0408767102] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We propose that the forward and reverse halves of a flash-induced protein-protein electron transfer (ET) photocycle should exhibit differential responses to dynamic interconversion of configurations when the most stable configuration is not the most reactive, because the reactants exist in different initial configurations: the flash-photoinitiated forward ET process begins with the protein partners in an equilibrium ensemble of configurations, many of which have little or no reactivity, whereas the reactant of the thermal back ET (the charge-separated intermediate) is formed in a nonequilibrium, "activated" protein configuration. We report evidence for this proposal in measurements on (i) mixed-metal hemoglobin hybrids, (ii) the complex between cytochrome c peroxidase and cytochrome c, and (iii and iv) the complexes of myoglobin and isolated hemoglobin alpha-chains with cytochrome b(5). For all three systems, forward and reverse ET does respond differently to modulation of dynamic processes; further, the response to changes in viscosity is different for each system.
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Affiliation(s)
- Brian M Hoffman
- Department of Chemistry, Northwestern University, 2145 North Sheridan Road, Evanston, IL 60208-3113, USA.
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Hirota S, Okumura H, Arie S, Tanaka K, Shionoya M, Takabe T, Funasaki N, Watanabe Y. Interaction of plastocyanin with oligopeptides: effect of lysine distribution within the peptide. J Inorg Biochem 2004; 98:849-55. [PMID: 15134931 DOI: 10.1016/j.jinorgbio.2003.10.022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2003] [Revised: 10/22/2003] [Accepted: 10/31/2003] [Indexed: 11/29/2022]
Abstract
We synthesized and purified four oligopeptides containing four lysines (KKKK, GKKGGKK, KKGGGKK, and KGKGKGK) as models for the plastocyanin (PC) interacting site of cytochrome f. These peptides competitively inhibited electron transfer between cytochrome c and PC. The inhibitory effect increased as the peptide concentrations were increased. The association constants between PC and the peptides did not differ significantly (3500-5100 M(-1)), although the association constant of PC-KGKGKGK was a little larger than the constants between PC and other peptides. Changes in the absorption spectrum of PC were observed when the peptides were added to the PC solution: peaks and troughs were detected at about 460 and 630 nm and at about 560 and 700 nm, respectively, in the difference absorption spectra between the spectra with and without peptides. These changes were attributed to the structural change at the copper site of PC by interaction with the peptides. The structural change was most significant when tetralysine was used. These results show that binding of the oligopeptide to PC is slightly more efficient when lysines are distributed uniformly within the peptide, whereas the structural change of PC becomes larger when the lysines are close to each other within the peptide.
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Affiliation(s)
- Shun Hirota
- Department of Physical Chemistry, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan.
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Dolidze TD, Khoshtariya DE, Waldeck DH, Macyk J, van Eldik R. Positive Activation Volume for a Cytochrome C Electrode Process: Evidence for a “Protein Friction” Mechanism from High-Pressure Studies. J Phys Chem B 2003. [DOI: 10.1021/jp035184t] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | | | - David H. Waldeck
- Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
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Khoshtariya DE, Wei J, Liu H, Yue H, Waldeck DH. Charge-transfer mechanism for cytochrome c adsorbed on nanometer thick films. Distinguishing frictional control from conformational gating. J Am Chem Soc 2003; 125:7704-14. [PMID: 12812512 DOI: 10.1021/ja034719t] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Using nanometer thick tunneling barriers with specifically attached cytochrome c, the electron-transfer rate constant was studied as a function of the SAM composition (alkane versus terthiophene), the omega-terminating group type (pyridine, imidazole, nitrile), and the solution viscosity. At large electrode-reactant separations, the pyridine terminated alkanethiols exhibit an exponential decline of the rate constant with increasing electron-transfer distance. At short separations, a plateau behavior, analogous to systems involving -COOH terminal groups to which cytochrome c can be attached electrostatically, is observed. The dependence of the rate constant in the plateau region on system properties is investigated. The rate constant is insensitive to the mode of attachment to the surface but displays a significant viscosity dependence, change with spacer composition (alkane versus terthiophene), and nature of the solvent (H(2)O versus D(2)O). Based on these findings and others, the conclusion is drawn that the charge-transfer rate constant at short distance is determined by polarization relaxation processes in the structure, rather than the electron tunneling probability or large-amplitude conformational rearrangement (gating). The transition in reaction mechanism with distance reflects a gradual transition between the tunneling and frictional mechanisms. This conclusion is consistent with data from a number of other sources as well.
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Jeuken LJC. Conformational reorganisation in interfacial protein electron transfer. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1604:67-76. [PMID: 12765764 DOI: 10.1016/s0005-2728(03)00026-4] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Protein-protein electron transfer (ET) plays an essential role in all redox chains. Earlier studies which used cross-linking and increased solution viscosity indicated that the rate of many ET reactions is limited (i.e., gated) by conformational reorientations at the surface interface. These results are later supported by structural studies using NMR and molecular modelling. New insights into conformational gating have also come from electrochemical experiments in which proteins are noncovalently adsorbed on the electrode surface. These systems have the advantage that it is relatively easy to vary systematically the driving force and electronic coupling. In this review we summarize the current knowledge obtained from these electrochemical experiments and compare it with some of the results obtained for protein-protein ET.
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Hirota S, Yamauchi O. Weak interactions and molecular recognition in systems involving electron transfer proteins. CHEM REC 2002; 1:290-9. [PMID: 11893069 DOI: 10.1002/tcr.1014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Electrostatic interactions and other weak interactions between amino acid side chains on protein surfaces play important roles in molecular recognition, and the mechanism of their intermolecular interactions has gained much interest. We established that charged peptides are useful for investigating the molecular recognition character of proteins and their molecular interaction induced structural changes. Positively charged lysine peptides competitively inhibited electron transfer from reduced cytochrome f (cyt f or cytochrome c (cyt c) to oxidized plastocyanin (PC), due to neutralization of the negatively charged site of PC by formation of PC-lysine peptide complexes. Lysine peptides also inhibited electron transfer from cyt c to cytochrome c peroxidase. Likewise, negatively charged aspartic acid peptides interacted with the positively charged sites of cytfand cyt c, and competitively inhibited electron transfer from reduced cytfor cyt c to oxidized PC and from [Fe(CN)6]4- to oxidized cyt c. Changes in the geometry and a shift to a higher redox potential of the active site Cu of PC on oligolysine binding were detected by spectroscopic and electrochemical measurements, owing to the absence of absorption in the visible region for lysine peptides. Structural and redox potential changes were also observed for cyt f and cyt c by interaction with aspartic acid peptides.
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Affiliation(s)
- S Hirota
- Department of Chemistry, Graduate School of Science, Nagoya University, Japan.
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Niki K, Sprinkle JR, Margoliash E. Intermolecular biological electron transfer: an electrochemical approach. Bioelectrochemistry 2002; 55:37-40. [PMID: 11786336 DOI: 10.1016/s1567-5394(01)00157-8] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We investigated the electron transfer (ET) rates between a well-defined gold electrode and cytochrome c immobilized at the carboxylic acid terminus of alkanethiol self-assembled monolayers (SAMs) by using the potential modulated electroreflectance technique. A logarithmic plot of ET rates against the chain length of the alkanethiol is linear with long chain alkanethiols. The ET rates become independent of the chain length with short alkanethiols. It is proposed that the rate-limiting ET step through short alkyl chains results from a configurational rearrangement process preceding the ET event. This "gating" process arises from a rearrangement of the cytochrome c from a thermodynamically stable binding form on the carboxylic acid terminus to a configuration, which facilitates the most efficient ET pathways (surface diffusion process). We propose that the lysine-13 of mammalian cytochrome c facilitates the most efficient ET pathway to the carboxylate terminus and this proposal is supported by the ET reaction rate of a rat cytochrome c mutant (RC9-K13A) [Elektrokhimiya (2001) in press], in which lysine-13 is replaced by alanine. The ET rate of K13A is more than six orders of magnitude smaller than that of the native protein.
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Affiliation(s)
- Katsumi Niki
- Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA.
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Hitomi Y, Hayashi T, Wada K, Mizutani T, Hisaeda Y, Ogoshi H. Interprotein Electron Transfer Reaction Regulated by an Artificial Interface We thank Prof. Dr. I. Morishima and his group for the arrangement of laser flash photolysis equipment. This work was supported by Nagase Science and Technology Foundation, and a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture, Japan. Y. H. was supported by Research Fellowships of the Japanese Society for the Promotion of Science for Young Scientists. Angew Chem Int Ed Engl 2001; 40:1098-1101. [PMID: 11268087 DOI: 10.1002/1521-3773(20010316)40:6<1098::aid-anie10980>3.0.co;2-g] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Yutaka Hitomi
- Department of Synthetic Chemistry and Biological Chemistry Graduate School of Engineering, Kyoto University Kyoto 606-8501 (Japan)
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Hitomi Y, Hayashi T, Wada K, Mizutani T, Hisaeda Y, Ogoshi H. Interprotein Electron Transfer Reaction Regulated by an Artificial Interface. Angew Chem Int Ed Engl 2001. [DOI: 10.1002/1521-3757(20010316)113:6<1132::aid-ange11320>3.0.co;2-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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39
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Metzler DE, Metzler CM, Sauke DJ. Transition Metals in Catalysis and Electron Transport. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50019-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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40
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Tremain SM, Kostić NM. Fate of the excited triplet state of zinc cytochrome c in the presence of iron(III), iron(II), iron-free, and heme-free forms of cytochrome c. Inorganica Chim Acta 2000. [DOI: 10.1016/s0020-1693(00)00012-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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41
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Avila A, Gregory BW, Niki K, Cotton TM. An Electrochemical Approach to Investigate Gated Electron Transfer Using a Physiological Model System: Cytochrome c Immobilized on Carboxylic Acid-Terminated Alkanethiol Self-Assembled Monolayers on Gold Electrodes. J Phys Chem B 2000. [DOI: 10.1021/jp992591p] [Citation(s) in RCA: 226] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Albert Avila
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, and Department of Chemistry, Illinois State University, Normal, Illinois 61790
| | - Brian W. Gregory
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, and Department of Chemistry, Illinois State University, Normal, Illinois 61790
| | - Katsumi Niki
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, and Department of Chemistry, Illinois State University, Normal, Illinois 61790
| | - Therese M. Cotton
- Department of Chemistry, Iowa State University, Ames, Iowa 50011, and Department of Chemistry, Illinois State University, Normal, Illinois 61790
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Hyun YL, Zhu Z, Davidson VL. Gated and ungated electron transfer reactions from aromatic amine dehydrogenase to azurin. J Biol Chem 1999; 274:29081-6. [PMID: 10506161 DOI: 10.1074/jbc.274.41.29081] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Interprotein electron transfer (ET) occurs between the tryptophan tryptophylquinone (TTQ) prosthetic group of aromatic amine dehydrogenase (AADH) and copper of azurin. The ET reactions from two chemically distinct reduced forms of TTQ were studied: an O-quinol form that was generated by reduction by dithionite, and an N-quinol form that was generated by reduction by substrate. It was previously shown that on reduction by substrate, an amino group displaces a carbonyl oxygen on TTQ, and that this significantly alters the rate of its oxidation by azurin (Hyun, Y-L., and Davidson V. L. (1995) Biochemistry 34, 12249-12254). To determine the basis for this change in reactivity, comparative kinetic and thermodynamic analyses of the ET reactions from the O-quinol and N-quinol forms of TTQ in AADH to the copper of azurin were performed. The reaction of the O-quinol exhibited values of electronic coupling (H(AB)) of 0.13 cm(-1) and reorganizational energy (lambda) of 1.6 eV, and predicted an ET distance of approximately 15 A. These results are consistent with the ET event being the rate-determining step for the redox reaction. Analysis of the reaction of the N-quinol by Marcus theory yielded an H(AB) which exceeded the nonadiabatic limit and predicted a negative ET distance. These results are diagnostic of a gated ET reaction. Solvent deuterium kinetic isotope effects of 1.5 and 3.2 were obtained, respectively, for the ET reactions from O-quinol and N-quinol AADH indicating that transfer of an exchangeable proton was involved in the rate-limiting reaction step which gates ET from the N-quinol, but not the O-quinol. These results are compared with those for the ET reactions from another TTQ enzyme, methylamine dehydrogenase, to amicyanin. The mechanism by which the ET reaction of the N-quinol is gated is also related to mechanisms of other gated interprotein ET reactions.
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Affiliation(s)
- Y L Hyun
- Department of Biochemistry, The University of Mississippi Medical Center, Jackson, Mississippi 39216-4505, USA
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Ivković-Jensen MM, Ullmann GM, Crnogorac MM, Ejdebäck M, Young S, Hansson O, Kostić NM. Comparing the rates and the activation parameters for the forward reaction between the triplet state of zinc cytochrome c and cupriplastocyanin and the back reaction between the zinc cytochrome c cation radical and cuproplastocyanin. Biochemistry 1999; 38:1589-97. [PMID: 9931026 DOI: 10.1021/bi9817156] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This is a comparative study of the photoinduced (so-called forward) electron-transfer reaction 3Zncyt/pc(II) --> Zncyt+/pc(I), between the triplet state of zinc cytochrome c (3Zncyt) and cupriplastocyanin [pc(II)], and the thermal (so-called back) electron-transfer reaction Zncyt+/pc(I) --> Zncyt/pc(II), between the cation (radical) of zinc cytochrome c (Zncyt+) and cuproplastocyanin [pc(I)], which follows it. Both reactions occur between associated (docked) reactants, and the respective unimolecular rate constants are kF and kB. Our previous studies showed that the forward reaction is gated by a rearrangement of the diprotein complex. Now we examine the back reaction and complare the two. We study the effects of temperature (in the range 273.3-302.9 K) and viscosity (in the range 1.00-17.4 cP) on the rate constants and determine enthalpies (DeltaH), entropies (DeltaS), and free energies (DeltaG) of activation. We compare wild-type spinach plastocyanin, the single mutants Tyr83Leu and Glu59Lys, and the double mutant Glu59Lys/Glu60Gln. The rate constant kB for wild-type spinach plastocyanin and its mutants markedly depends on viscosity, an indication that the back reaction is also gated. The activation parameters DeltaH and DeltaS show that the forward and back reactions have similar mechanisms, involving a rearrangement of the diprotein complex from the initial binding configuration to the reactive configuration. The rearrangements of the complexes 3Zncyt/pc(II) and Zncyt+/pc(I) that gate their respective reactions are similar but not identical. Since the back reaction of all plastocyanin variants is faster than the forward reaction, the difference in free energy between the docking and the reactive configuration is smaller for the back reaction than for the forward reaction. This difference is explained by the change in the electrostatic potential on the plastocyanin surface as Cu(II) is reduced to Cu(I). It is the smaller DeltaH that makes DeltaG smaller for the back reaction than for the forward reaction.
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Ivković-Jensen MM, Ullmann GM, Young S, Hansson O, Crnogorac MM, Ejdebäck M, Kostić NM. Effects of single and double mutations in plastocyanin on the rate constant and activation parameters for the rearrangement gating the electron-transfer reaction between the triplet state of zinc cytochrome c and cupriplastocyanin. Biochemistry 1998; 37:9557-69. [PMID: 9649339 DOI: 10.1021/bi9802871] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The unimolecular rate constant for the photoinduced electron-transfer reaction 3Zncyt/pc(II) --> Zncyt+/pc(I) within the electrostatic complex of zinc cytochrome c and spinach cupriplastocyanin is kF. We report the effects on kF of the following factors, all at pH 7.0: 12 single mutations on the plastocyanin surface (Leu12Asn, Leu12Glu, Leu12Lys, Asp42Asn, Asp42Lys, Glu43Asn, Glu59Gln, Glu59Lys, Glu60Gln, Glu60Lys, Gln88Glu, and Gln88Lys), the double mutation Glu59Lys/Glu60Gln, temperature (in the range 273.3-302.9 K), and solution viscosity (in the range 1. 00-116.0 cP) at 283.2 and 293.2 K. We also report the effects of the plastocyanin mutations on the association constant (Ka) and the corresponding free energy of association (DeltaGa) with zinc cytochrome c at 298.2 K. Dependence of kF on temperature yielded the activation parameters DeltaH, DeltaS, and DeltaG. Dependence of kF on solution viscosity yielded the protein friction and confirmed the DeltaG values determined from the temperature dependence. The aforementioned intracomplex reaction is not a simple electron-transfer reaction because donor-acceptor electronic coupling (HAB) and reorganizational energy (lambda), obtained by fitting of the temperature dependence of kF to the Marcus equation, deviate from the expectations based on precedents and because kF greatly depends on viscosity. This last dependence and the fact that certain mutations affect Ka but not kF are two lines of evidence against the mechanism in which the electron-transfer step is coupled with the faster, but thermodynamically unfavorable, rearrangement step. The electron-transfer reaction is gated by the slower, and thus rate determining, structural rearrangement of the diprotein complex; the rate constant kF corresponds to this rearrangement. Isokinetic correlation of DeltaH and DeltaS parameters and Coulombic energies of the various configurations of the Zncyt/pc(II) complex consistently show that the rearrangement is a facile configurational fluctuation of the associated proteins, qualitatively the same process regardless of the mutations in plastocyanin. Correlation of kF with the orientation of the cupriplastocyanin dipole moment indicates that the reactive configuration of the diprotein complex involves the area near the residue 59, between the upper acidic cluster and the hydrophobic patch. Kinetic effects and noneffects of plastocyanin mutations show that the rearrangement from the initial (docking) configuration, which involves both acidic clusters, to the reactive configuration does not involve the lower acidic cluster and the hydrophobic patch but involves the upper acidic cluster and the area near the residue 88.
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