1
|
Yu X, Lovrincic R, Sepunaru L, Li W, Vilan A, Pecht I, Sheves M, Cahen D. Insights into Solid-State Electron Transport through Proteins from Inelastic Tunneling Spectroscopy: The Case of Azurin. ACS NANO 2015; 9:9955-63. [PMID: 26381112 DOI: 10.1021/acsnano.5b03950] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Surprisingly efficient solid-state electron transport has recently been demonstrated through "dry" proteins (with only structural, tightly bound H2O left), suggesting proteins as promising candidates for molecular (bio)electronics. Using inelastic electron tunneling spectroscopy (IETS), we explored electron-phonon interaction in metal/protein/metal junctions, to help understand solid-state electronic transport across the redox protein azurin. To that end an oriented azurin monolayer on Au is contacted by soft Au electrodes. Characteristic vibrational modes of amide and amino acid side groups as well as of the azurin-electrode contact were observed, revealing the azurin native conformation in the junction and the critical role of side groups in the charge transport. The lack of abrupt changes in the conductance and the line shape of IETS point to far off-resonance tunneling as the dominant transport mechanism across azurin, in line with previously reported (and herein confirmed) azurin junctions. The inelastic current and hence electron-phonon interaction appear to be rather weak and comparable in magnitude with the inelastic fraction of tunneling current via alkyl chains, which may reflect the known structural rigidity of azurin.
Collapse
Affiliation(s)
| | - Robert Lovrincic
- Institute for High Frequency Technology, TU Braunschweig, and Innovationlab , Speyerer Str. 4, 69115 Heidelberg, Germany
| | | | | | | | | | | | | |
Collapse
|
2
|
Krishtalik LI. The medium reorganization energy for the charge transfer reactions in proteins. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:1444-56. [DOI: 10.1016/j.bbabio.2011.07.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2011] [Revised: 06/30/2011] [Accepted: 07/04/2011] [Indexed: 10/18/2022]
|
3
|
Copper Proteins as Model Systems for Investigating Intramolecular Electron Transfer Processes. ADVANCES IN CHEMICAL PHYSICS 2007. [DOI: 10.1002/9780470141663.ch10] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2023]
|
4
|
|
5
|
|
6
|
Bixon M, Jortner J. Electron Transfer-from Isolated Molecules to Biomolecules. ADVANCES IN CHEMICAL PHYSICS 2007. [DOI: 10.1002/9780470141656.ch3] [Citation(s) in RCA: 232] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
|
7
|
Machczynski MC, Kuhl KP, McGuirl MA. Modulation of the electrochemical behavior of tyrosyl radicals by the electrode surface. Anal Biochem 2007; 362:89-97. [PMID: 17254538 DOI: 10.1016/j.ab.2006.11.040] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2006] [Revised: 11/22/2006] [Accepted: 11/30/2006] [Indexed: 11/20/2022]
Abstract
The ability to adsorb proteins and enzymes on electrode surfaces enhances opportunities for studying enzyme activity and redox-based catalysis. Proteins may be bound in a chosen orientation on surfaces so that specific sites within them may be preferentially studied, but to date no systematic study of a redox moiety from solvent to electrode surface to the protein milieu has been performed. We report the redox and ionization behavior of tyrosine-cysteine, using the cysteine residue to form covalent linkages with Au and self-assembled-monolayer (SAM)-modified Au surfaces and using the tyrosine for redox activity. In addition, the same redox fragment incorporated into a protein bound to a SAM is examined. We find that directly binding the dipeptide to Au causes the greatest change in properties, while binding it to the SAM causes a slight perturbation in redox potential and a significant perturbation in pK(a). When azurin with a surface-exposed tyrosine is bound to a SAM-modified electrode, the redox potential and pK(a) of the tyrosine are nearly unperturbed from the values found for the dipeptide free in solution. Finally, quantification of the voltammetric signal indicates that tyrosine oxidation in the protein triggers the additional oxidation of another nearby amino acid.
Collapse
Affiliation(s)
- Michael C Machczynski
- Division of Biological Sciences and Biomolecular Structure and Dynamics Program, The University of Montana, Missoula, MT 59812, USA
| | | | | |
Collapse
|
8
|
Corvis Y, Brezesinski G, Rink R, Walcarius A, Van der Heyden A, Mutelet F, Rogalska E. Analytical Investigation of the Interactions between SC3 Hydrophobin and Lipid Layers: Elaborating of Nanostructured Matrixes for Immobilizing Redox Systems. Anal Chem 2006; 78:4850-64. [PMID: 16841903 DOI: 10.1021/ac0602064] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hydrophobins are highly tensioactive fungal proteins with a pronounced affinity for interfaces and a propensity for self-assembly. Recently, these proteins were shown to be useful in retaining different molecules on solid surfaces. This finding offers a possibility for developing new functional materials, while creating the necessity of further research at a deeper mechanistic level. In this work, the mechanisms governing the surface phenomena were studied using native Schizophyllum commune hydrophobin (SC3) and lipid mono- and bilayers; the soft matter systems were used to get a handle on the interactive protein/interface effects at a molecular level. The results obtained indicated that the SC3/lipid membrane interactions were adjusted by protein conformational adaptation, allowing its incorporation into lipid matrixes; the incorporation of a chelating SC3 hydrophobin (PFA-SC3) in a monoolein cubic phase yielded a biomimetic, cell-like system of Cu(II) cation immobilization. This system, which is suitable for modifying electrode surface and monitoring the Cu(II)/Cu(0) redox process, may be of practical interest in switching and sensing.
Collapse
Affiliation(s)
- Yohann Corvis
- Groupe d'Etude des Vecteurs Supramoléculaires du Médicament UMR 7565 CNRS/Université Henri Poincaré Nancy 1, Faculté des Sciences, BP 239, 54506 Vandoeuvre-lès-Nancy Cedex, France
| | | | | | | | | | | | | |
Collapse
|
9
|
Seyedsayamdost MR, Yee CS, Reece SY, Nocera DG, Stubbe J. pH Rate profiles of FnY356-R2s (n = 2, 3, 4) in Escherichia coli ribonucleotide reductase: evidence that Y356 is a redox-active amino acid along the radical propagation pathway. J Am Chem Soc 2006; 128:1562-8. [PMID: 16448127 DOI: 10.1021/ja055927j] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The Escherichia coli ribonucleotide reductase (RNR), composed of two subunits (R1 and R2), catalyzes the conversion of nucleotides to deoxynucleotides. Substrate reduction requires that a tyrosyl radical (Y(122)*) in R2 generate a transient cysteinyl radical (C(439)*) in R1 through a pathway thought to involve amino acid radical intermediates [Y(122)* --> W(48) --> Y(356) within R2 to Y(731) --> Y(730) --> C(439) within R1]. To study this radical propagation process, we have synthesized R2 semisynthetically using intein technology and replaced Y(356) with a variety of fluorinated tyrosine analogues (2,3-F(2)Y, 3,5-F(2)Y, 2,3,5-F(3)Y, 2,3,6-F(3)Y, and F(4)Y) that have been described and characterized in the accompanying paper. These fluorinated tyrosine derivatives have potentials that vary from -50 to +270 mV relative to tyrosine over the accessible pH range for RNR and pK(a)s that range from 5.6 to 7.8. The pH rate profiles of deoxynucleotide production by these F(n)()Y(356)-R2s are reported. The results suggest that the rate-determining step can be changed from a physical step to the radical propagation step by altering the reduction potential of Y(356)* using these analogues. As the difference in potential of the F(n)()Y* relative to Y* becomes >80 mV, the activity of RNR becomes inhibited, and by 200 mV, RNR activity is no longer detectable. These studies support the model that Y(356) is a redox-active amino acid on the radical-propagation pathway. On the basis of our previous studies with 3-NO(2)Y(356)-R2, we assume that 2,3,5-F(3)Y(356), 2,3,6-F(3)Y(356), and F(4)Y(356)-R2s are all deprotonated at pH > 7.5. We show that they all efficiently initiate nucleotide reduction. If this assumption is correct, then a hydrogen-bonding pathway between W(48) and Y(356) of R2 and Y(731) of R1 does not play a central role in triggering radical initiation nor is hydrogen-atom transfer between these residues obligatory for radical propagation.
Collapse
Affiliation(s)
- Mohammad R Seyedsayamdost
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA
| | | | | | | | | |
Collapse
|
10
|
Seyedsayamdost MR, Reece SY, Nocera DG, Stubbe J. Mono-, Di-, Tri-, and Tetra-Substituted Fluorotyrosines: New Probes for Enzymes That Use Tyrosyl Radicals in Catalysis†. J Am Chem Soc 2006; 128:1569-79. [PMID: 16448128 DOI: 10.1021/ja055926r] [Citation(s) in RCA: 113] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A set of N-acylated, carboxyamide fluorotyrosine (F(n)()Y) analogues [Ac-3-FY-NH(2), Ac-3,5-F(2)Y-NH(2), Ac-2,3-F(2)Y-NH(2), Ac-2,3,5-F(3)Y-NH(2), Ac-2,3,6-F(3)Y-NH(2) and Ac-2,3,5,6-F(4)Y-NH(2)] have been synthesized from their corresponding amino acids to interrogate the detailed reaction mechanism(s) accessible to F(n)()Y*s in small molecules and in proteins. These Ac-F(n)()Y-NH(2) derivatives span a pK(a) range from 5.6 to 8.4 and a reduction potential range of 320 mV in the pH region accessible to most proteins (6-9). DFT electronic-structure calculations capture the observed trends for both the reduction potentials and pK(a)s. Dipeptides of the methyl ester of 4-benzoyl-l-phenylalanyl-F(n)()Ys at pH 4 were examined with a nanosecond laser pulse and transient absorption spectroscopy to provide absorption spectra of F(n)()Y*s. The EPR spectrum of each F(n)()Y* has also been determined by UV photolysis of solutions at pH 11 and 77 K. The ability to vary systematically both pK(a) and radical reduction potential, together with the facility to monitor radical formation with distinct absorption and EPR features, establishes that F(n)()Ys will be useful in the study of biological charge-transport mechanisms involving tyrosine. To demonstrate the efficacy of the fluorotyrosine method in unraveling charge transport in complex biological systems, we report the global substitution of tyrosine by 3-fluorotyrosine (3-FY) in the R2 subunit of ribonucleotide reductase (RNR) and present the EPR spectrum along with its simulation of 3-FY122*. In the companion paper, we demonstrate the utility of F(n)()Ys in providing insight into the mechanism of tyrosine oxidation in biological systems by incorporating them site-specifically at position 356 in the R2 subunit of Escherichia coli RNR.
Collapse
Affiliation(s)
- Mohammad R Seyedsayamdost
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA
| | | | | | | |
Collapse
|
11
|
Reece SY, Nocera DG. Direct Tyrosine Oxidation Using the MLCT Excited States of Rhenium Polypyridyl Complexes. J Am Chem Soc 2005; 127:9448-58. [PMID: 15984872 DOI: 10.1021/ja0510360] [Citation(s) in RCA: 119] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Rhenium(I) polypyridyl complexes have been designed for the intramolecular photogeneration of tyrosyl radical. Tyrosine (Y) and phenylalanine (F) have each been separately appended to a conventional Re(I)(bpy)(CO)(3)CN framework via an amide linkage to the bipyridine (bpy) ligand. Comparative time-resolved emission quenching and transient absorption spectra of Re(bpy-Y)(CO)(3)CN and Re(bpy-F)(CO)(3)CN show that Y is oxidized only upon its deprotonation at pH 12. In an effort to redirect electron transport so that it is more compatible with intramolecular Y oxidation, polypyridyl Re(I) complexes have been prepared with the amide bond functionality located on a pendant phosphine ligand. A [Re(phen)(PP-Bn)(CO)(2)](PF(6)) (PP = bis(diphenylphosphino)ethylene) complex has been synthesized and crystallographically characterized. Electrochemistry and phosphorescence measurements of this complex indicate a modest excited-state potential for tyrosine oxidation, similar to that for the (bpy)Re(I)(CO)(3)CN framework. The excited-state oxidation potential can be increased by introducing a monodentate phosphine to the Re(I)(NN)(CO)(3)(+) framework (NN = polypyridyl). In this case, Y is oxidized at all pHs when appended to the triphenylphosphine (P) of [Re(phen)(P-Y)(CO(3))](PF(6)). Analysis of the pH dependence of the rate constant for tyrosyl radical generation is consistent with a proton-coupled electron transfer (PCET) quenching mechanism.
Collapse
Affiliation(s)
- Steven Y Reece
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307, USA
| | | |
Collapse
|
12
|
Voltammetric measurement of Michaelis–Menten kinetics for a protein in a lipid film reacting with a protein in solution. Electrochem commun 2005. [DOI: 10.1016/j.elecom.2004.12.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
|
13
|
Stubbe J, Nocera DG, Yee CS, Chang MCY. Radical initiation in the class I ribonucleotide reductase: long-range proton-coupled electron transfer? Chem Rev 2003; 103:2167-201. [PMID: 12797828 DOI: 10.1021/cr020421u] [Citation(s) in RCA: 666] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- JoAnne Stubbe
- Department of Chemistry, 77 Massachusetts Avenue, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA.
| | | | | | | |
Collapse
|
14
|
|
15
|
Farver O, Einarsdóttir O, Pecht I. Electron transfer rates and equilibrium within cytochrome c oxidase. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:950-4. [PMID: 10672001 DOI: 10.1046/j.1432-1327.2000.01072.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Intramolecular electron transfer (ET) between the CuA center and heme a in bovine cytochrome c oxidase was investigated by pulse radiolysis. CuA, the initial electron acceptor, was reduced by 1-methyl nicotinamide radicals in a diffusion-controlled reaction, as monitored by absorption changes at 830 nm. After the initial reduction phase, the 830 nm absorption was partially restored, corresponding to reoxidation of the CuA center. Concomitantly, the absorption at 445 nm and 605 nm increased, indicating reduction of heme a. The rate constants for heme a reduction and CuA reoxidation were identical within experimental error and independent of the enzyme concentration. This demonstrates that a fast intramolecular electron equilibration is taking place between CuA and heme a. The rate constants for CuA --> heme a ET and the reverse (heme a --> CuA) process were found to be 13 000 s-1 and 3700 s-1, respectively, at 25 degrees C and pH 7.4. This corresponds to an equilibrium constant of 3.4 under these conditions. Thermodynamic and activation parameters of the ET reactions were determined. The significance of these results, particularly the observed low activation barriers, are discussed within the framework of the known three-dimensional structure, ET pathways and reorganization energies.
Collapse
Affiliation(s)
- O Farver
- Institute of Analytical Chemistry, The Royal Danish School of Pharmacy, Copenhagen, Denmark.
| | | | | |
Collapse
|
16
|
Suzuki S, Kataoka K, Yamaguchi K, Inoue T, Kai Y. Structure–function relationships of copper-containing nitrite reductases. Coord Chem Rev 1999. [DOI: 10.1016/s0010-8545(99)00069-7] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
17
|
Casella L, Monzani E, Santagostini L, de Gioia L, Gullotti M, Fantucci P, Beringhelli T, Marchesini A. Inhibitor binding studies on ascorbate oxidase. Coord Chem Rev 1999. [DOI: 10.1016/s0010-8545(99)00014-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
18
|
Olsson MH, Ryde U, Roos BO. Quantum chemical calculations of the reorganization energy of blue-copper proteins. Protein Sci 1998; 7:2659-68. [PMID: 9865961 PMCID: PMC2143893 DOI: 10.1002/pro.5560071220] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The inner-sphere reorganization energy for several copper complexes related to the active site in blue-copper protein has been calculated with the density functional B3LYP method. The best model of the blue-copper proteins, Cu(Im)2(SCH3)(S(CH3)2)(0/+), has a self-exchange inner-sphere reorganization energy of 62 kJ/mol, which is at least 120 kJ/mol lower than for Cu(H2O)4(+/2+). This lowering of the reorganization energy is caused by the soft ligands in the blue-copper site, especially the cysteine thiolate and the methionine thioether groups. Soft ligands both make the potential surfaces of the complexes flatter and give rise to oxidized structures that are quite close to a tetrahedron (rather than tetragonal). Approximately half of the reorganization energy originates from changes in the copper-ligand bond lengths and half of this contribution comes from the Cu-S(Cys) bond. A tetragonal site, which is present in the rhombic type 1 blue-copper proteins, has a slightly higher (16 kJ/mol) inner-sphere reorganization energy than a trigonal site, present in the axial type 1 copper proteins. A site with the methionine ligand replaced by an amide group, as in stellacyanin, has an even higher reorganization energy, about 90 kJ/mol.
Collapse
Affiliation(s)
- M H Olsson
- Department of Theoretical Chemistry, Lund University, Chemical Centre, Sweden
| | | | | |
Collapse
|
19
|
Monzani E, Casella L, Zoppellaro G, Gullotti M, Pagliarin R, Bonomo RP, Tabbi G, Nardin G, Randaccio L. Synthetic models for biological trinuclear copper clusters. Trinuclear and binuclear complexes derived from an octadentate tetraamine-tetrabenzimidazole ligand. Inorganica Chim Acta 1998. [DOI: 10.1016/s0020-1693(98)00221-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
20
|
Williamson DA, Bowler BE. Electron Transfer through the Hydrogen-Bonded Interface of a β-Turn-Forming Depsipeptide. J Am Chem Soc 1998. [DOI: 10.1021/ja981384k] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- David A. Williamson
- Contribution from the Department of Chemistry and Biochemistry, 2190 East Iliff Avenue, University of Denver, Denver, Colorado 80208-2436
| | - Bruce E. Bowler
- Contribution from the Department of Chemistry and Biochemistry, 2190 East Iliff Avenue, University of Denver, Denver, Colorado 80208-2436
| |
Collapse
|
21
|
de Andrade PCP, Onuchic JN. Generalized pathway model to compute and analyze tunneling matrix elements in proteins. J Chem Phys 1998. [DOI: 10.1063/1.475828] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
22
|
|
23
|
|
24
|
Ghindilis AL, Atanasov P, Wilkins E. Enzyme-catalyzed direct electron transfer: Fundamentals and analytical applications. ELECTROANAL 1997. [DOI: 10.1002/elan.1140090902] [Citation(s) in RCA: 341] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
25
|
Wolfgang J, Risser SM, Priyadarshy S, Beratan DN. Secondary Structure Conformations and Long Range Electronic Interactions in Oligopeptides. J Phys Chem B 1997. [DOI: 10.1021/jp963771r] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
26
|
Hazzard JT, Maritano S, Tollin G, Marchesini A. Laser flash photolysis experiments on the effects of freezing and salt addition on intramolecular electron transfer within one-electron reduced ascorbate oxidase. Arch Biochem Biophys 1997; 339:24-32. [PMID: 9056229 DOI: 10.1006/abbi.1996.9860] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Laser flash photolysis has been used to investigate the effects of freezing protein solutions and of adding various salts on the kinetics of one-electron photoreduction by 5-deazariboflavin semiquinone (5-DRFH.) of oxidized ascorbate oxidase (AO) from zucchini in 100 mM phosphate buffer (pH 7.0). The initial reaction between oxidized AO and 5-DRFH. is quite rapid (k approximately 10(8) M-1 s-1) and occurs at the blue Type I Cu center. Subsequent to this, a slower, protein concentration-independent intramolecular reoxidation of the Type I Cu is observed, with kET approximately 150 s-1, resulting in 40-50% reoxidation of the blue Cu center and the establishment of an electron transfer (ET) equilibrium between the various Cu centers in AO. When such a sample of AO was frozen overnight at -30 degrees C, flash photolysis of the thawed sample showed no effect on the kinetics of reduction of the Type I Cu by 5-DRFH. However, the rate constant for intramolecular ET decreased to a value of 2.7 s-1, with only 20% reoxidation of the Type I center. Reduction of the enzyme with ascorbic acid, followed by O2 oxidation, resulted in restoration of rapid intramolecular reoxidation (kET = 130 s-1), with 33% of the Type I Cu reduced by 5-DRFH. being reoxidized. These results are consistent with previous work which showed that samples of AO with initially low activity can be reactivated by ascorbic acid turnover in the presence of O2. When AO was frozen in the presence of ascorbic acid, similar inhibition of intramolecular ET was obtained, whereas upon turnover of this sample by further addition of ascorbic acid and exposure to O2, activity was not restored. The effects of addition of (NH4)2SO4, Na2SO4, NH4Cl, NaCl, KCl, and KF on the kinetics of Type I Cu reduction by 5-deazariboflavin semiquinone and on the subsequent intramolecular ET were also examined. A twofold increase in the bimolecular rate constant for reduction of the Type I Cu was observed for the two sodium salts at high concentrations (500 mM). Intramolecular ET was also significantly affected upon addition of all three chloride salts. Although the intramolecular ET rate constant was not altered, the fraction of reduced Type I Cu reoxidized by the trinuclear cluster decreased with increasing Cl- concentration, regardless of the cation. Total inhibition of intramolecular ET was observed at a significantly lower concentration of KF than observed with the Cl- salts. Sulfate ion had no effect on either parameter. These changes are thus ion specific, suggesting that they are related to ion binding by the protein, possibly at one of the coppers of the trinuclear cluster.
Collapse
Affiliation(s)
- J T Hazzard
- Department of Biochemistry, University of Arizona, Tucson 85721, USA
| | | | | | | |
Collapse
|
27
|
McCleskey TM, Mizoguchi TJ, Richards JH, Gray HB. Electronic Spectroscopy of Gold(I) Pseudomonasaeruginosa Azurin Derivatives. Inorg Chem 1996; 35:3434-3435. [PMID: 11666550 DOI: 10.1021/ic951055i] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- T. Mark McCleskey
- Beckman Institute, California Institute of Technology, Pasadena, California 91125
| | | | | | | |
Collapse
|
28
|
Structure-function correlation of intramolecular electron transfer in wild type and single-site mutated azurins. Chem Phys 1996. [DOI: 10.1016/0301-0104(95)00294-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
29
|
Jin W, Wollenberger U, Bier FF, Makower A, Scheller FW. Electron transfer between cytochrome c and copper enzymes. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/0302-4598(95)01879-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
30
|
|
31
|
Curry WB, Grabe MD, Kurnikov IV, Skourtis SS, Beratan DN, Regan JJ, Aquino AJ, Beroza P, Onuchic JN. Pathways, pathway tubes, pathway docking, and propagators in electron transfer proteins. J Bioenerg Biomembr 1995; 27:285-93. [PMID: 8847342 DOI: 10.1007/bf02110098] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The simplest views of long-range electron transfer utilize flat one-dimensional barrier tunneling models, neglecting structural details of the protein medium. The pathway model of protein electron transfer reintroduces structure by distinguishing between covalent bonds, hydrogen bonds, and van der Waals contacts. These three kinds of interactions in a tunneling pathway each have distinctive decay factors associated with them. The distribution and arrangement of these bonded and nonbonded contacts in a folded protein varies tremendously between structures, adding a richness to the tunneling problem that is absent in simpler views. We review the pathway model and the predictions that it makes for protein electron transfer rates in small proteins, docked proteins, and the photosynthetic reactions center. We also review the formulation of the protein electron transfer problem as an effective two-level system. New multi-pathway approaches and improved electronic Hamiltonians are described briefly as well.
Collapse
Affiliation(s)
- W B Curry
- Department of Chemistry, University of Pittsburgh, Pennsylvania 15260, USA
| | | | | | | | | | | | | | | | | |
Collapse
|