1
|
Hewitt SH, Filby MH, Hayes E, Kuhn LT, Kalverda AP, Webb ME, Wilson AJ. Protein Surface Mimetics: Understanding How Ruthenium Tris(Bipyridines) Interact with Proteins. Chembiochem 2016; 18:223-231. [PMID: 27860106 PMCID: PMC5347857 DOI: 10.1002/cbic.201600552] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Indexed: 12/21/2022]
Abstract
Protein surface mimetics achieve high-affinity binding by exploiting a scaffold to project binding groups over a large area of solvent-exposed protein surface to make multiple cooperative noncovalent interactions. Such recognition is a prerequisite for competitive/orthosteric inhibition of protein-protein interactions (PPIs). This paper describes biophysical and structural studies on ruthenium(II) tris(bipyridine) surface mimetics that recognize cytochrome (cyt) c and inhibit the cyt c/cyt c peroxidase (CCP) PPI. Binding is electrostatically driven, with enhanced affinity achieved through enthalpic contributions thought to arise from the ability of the surface mimetics to make a greater number of noncovalent interactions than CCP with surface-exposed basic residues on cyt c. High-field natural abundance 1 H,15 N HSQC NMR experiments are consistent with surface mimetics binding to cyt c in similar manner to CCP. This provides a framework for understanding recognition of proteins by supramolecular receptors and informing the design of ligands superior to the protein partners upon which they are inspired.
Collapse
Affiliation(s)
- Sarah H Hewitt
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK.,Astbury Centre For Structural Molecular Biology, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
| | - Maria H Filby
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK.,Astbury Centre For Structural Molecular Biology, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
| | - Ed Hayes
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK.,Astbury Centre For Structural Molecular Biology, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
| | - Lars T Kuhn
- Astbury Centre For Structural Molecular Biology, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
| | - Arnout P Kalverda
- Astbury Centre For Structural Molecular Biology, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
| | - Michael E Webb
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK.,Astbury Centre For Structural Molecular Biology, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
| | - Andrew J Wilson
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK.,Astbury Centre For Structural Molecular Biology, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
| |
Collapse
|
2
|
Volkov AN, Nicholls P, Worrall JA. The complex of cytochrome c and cytochrome c peroxidase: The end of the road? BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:1482-503. [DOI: 10.1016/j.bbabio.2011.07.010] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Revised: 07/21/2011] [Accepted: 07/22/2011] [Indexed: 11/25/2022]
|
3
|
Shifting the equilibrium between the encounter state and the specific form of a protein complex by interfacial point mutations. J Am Chem Soc 2010; 132:11487-95. [PMID: 20672804 DOI: 10.1021/ja100867c] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Recent experimental studies have confirmed a long-held view that protein complex formation proceeds via a short-lived encounter state. The population of this transient intermediate, stabilized mainly by long-range electrostatic interactions, varies among different complexes. Here we show that the occupancy of the encounter state can be modulated across a broad range by single point mutations of interfacial residues. Using a combination of Monte Carlo simulations and paramagnetic relaxation enhancement NMR spectroscopy, we illustrate that it is possible to both enhance and diminish the binding specificity in an electron transfer complex of yeast cytochrome c (Cc) and cytochrome c peroxidase. The Cc T12A mutation decreases the population of the encounter to 10% as compared with 30% in the wild-type complex. More dramatically, the Cc R13A substitution reverses the relative occupancies of the stereospecific and the encounter forms, with the latter now being the dominant species with the population of 80%. This finding indicates that the encounter state can make a large contribution to the stability of a protein complex. Also, it appears that by adjusting the amount of the encounter through a judicious choice of point mutations, we can remodel the energy landscape of a protein complex and tune its binding specificity.
Collapse
|
4
|
Interaction of onconase with the human ribonuclease inhibitor protein. Biochem Biophys Res Commun 2008; 377:512-514. [PMID: 18930025 DOI: 10.1016/j.bbrc.2008.10.032] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2008] [Accepted: 10/02/2008] [Indexed: 11/21/2022]
Abstract
One of the tightest known protein-protein interactions in biology is that between members of the ribonuclease A superfamily and the ribonuclease inhibitor protein (RI). Some members of this superfamily are able to kill cancer cells, and the ability to evade RI is a major determinant of whether a ribonuclease will be cytotoxic. The archetypal cytotoxic ribonuclease, onconase (ONC), is in late-stage clinical trials for the treatment of malignant mesothelioma. We present here the first measurement of the inhibition of the ribonucleolytic activity of ONC by RI. This inhibition occurs with K(i)=0.15muM in a solution of low salt concentration.
Collapse
|
5
|
Erman JE, Vitello LB. Yeast cytochrome c peroxidase: mechanistic studies via protein engineering. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1597:193-220. [PMID: 12044899 DOI: 10.1016/s0167-4838(02)00317-5] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Cytochrome c peroxidase (CcP) is a yeast mitochondrial enzyme that catalyzes the reduction of hydrogen peroxide to water by ferrocytochrome c. It was the first heme enzyme to have its crystallographic structure determined and, as a consequence, has played a pivotal role in developing ideas about structural control of heme protein reactivity. Genetic engineering of the active site of CcP, along with structural, spectroscopic, and kinetic characterization of the mutant proteins has provided considerable insight into the mechanism of hydrogen peroxide activation, oxygen-oxygen bond cleavage, and formation of the higher-oxidation state intermediates in heme enzymes. The catalytic mechanism involves complex formation between cytochrome c and CcP. The cytochrome c/CcP system has been very useful in elucidating the complexities of long-range electron transfer in biological systems, including protein-protein recognition, complex formation, and intracomplex electron transfer processes.
Collapse
Affiliation(s)
- James E Erman
- Department of Chemistry and Biochemistry, Northern Illinois University, Normal Rd., DeKalb, IL 60115-2862, USA.
| | | |
Collapse
|
6
|
Nocek JM, Zhou JS, De Forest S, Priyadarshy S, Beratan DN, Onuchic JN, Hoffman BM. Theory and Practice of Electron Transfer within Proteinminus signProtein Complexes: Application to the Multidomain Binding of Cytochrome c by Cytochrome c Peroxidase. Chem Rev 1996; 96:2459-2490. [PMID: 11848833 DOI: 10.1021/cr9500444] [Citation(s) in RCA: 177] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Judith M. Nocek
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, and Department of Physics, University of California at San Diego, LaJolla, California 92093-0319
| | | | | | | | | | | | | |
Collapse
|
7
|
The cytochrome C peroxidase oxidation of ferrocytochrome C. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/s1057-8943(96)80006-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
|
8
|
Matthis AL, Vitello LB, Erman JE. Oxidation of yeast iso-1 ferrocytochrome c by yeast cytochrome c peroxidase compounds I and II. Dependence upon ionic strength. Biochemistry 1995; 34:9991-9. [PMID: 7632698 DOI: 10.1021/bi00031a022] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The reduction of cytochrome c peroxidase compound I by excess yeast iso-1 ferrocytochrome c is biphasic. Two pseudo-first-order rate constants can be measured by stopped-flow techniques. The fastest rate process is the reduction of cytochrome c peroxidase compound I to compound II, and the slower process is the reduction of II to the native enzyme. The yeast iso-1 ferrocytochrome c concentration dependence of the reduction of cytochrome c peroxidase compound I to compound II is consistent with a mechanism involving two binding sites for cytochrome c on cytochrome c peroxidase. Electron transfer from cytochrome c bound at the high-affinity binding site to the Fe(IV) site in cytochrome c peroxidase compound I is dependent upon ionic strength, increasing from 15 +/- 6 to 2000 +/- 100 s-1 over the ionic strength range 0.01-0.20 M. The reduction rate of the Fe(IV) site in the 2:1 yeast iso-1 ferrocytochrome c/cytochrome c peroxidase compound I complex is essentially independent of ionic strength with a value of 3800 +/- 300 s-1. The Fe(IV) site in cytochrome c peroxidase compound I is preferentially reduced by yeast ferrocytochrome c between 0.01 and 0.20 M ionic strength while the Trp-191 radical is preferentially reduced above 0.30 M ionic strength. The association rate constant for the binding of yeast iso-1 ferrocytochrome c to cytochrome c peroxidase compound I can be evaluated and varies from a remarkable 1 x 10(10) M-1 s-1 at 0.01 M ionic strength to 1.2 x 10(5) M-1 s-1 at 1.0 M ionic strength. Between 0.01 and 0.20 M ionic strength, the reduction of cytochrome c peroxidase compound II to the native enzyme is anomalous. The reaction is independent of the cytochrome c concentration and directly proportional to the initial cytochrome c peroxidase compound I concentration.
Collapse
Affiliation(s)
- A L Matthis
- Department of Chemistry, Northern Illinois University, DeKalb 60115, USA
| | | | | |
Collapse
|
9
|
Matthis AL, Erman JE. Cytochrome c peroxidase-catalyzed oxidation of yeast iso-1 ferrocytochrome c by hydrogen peroxide. Ionic strength dependence of the steady-state parameters. Biochemistry 1995; 34:9985-90. [PMID: 7632697 DOI: 10.1021/bi00031a021] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The cytochrome c peroxidase-catalyzed oxidation of yeast iso-1 ferrocytochrome c by hydrogen peroxide can be understood on the basis of a mechanism involving two cytochrome c-binding sites on cytochrome c peroxidase. Values of the equilibrium dissociation constants for both the high- and low-affinity binding sites determined from the steady-state kinetic measurements agree well with published values obtained by vastly different techniques, providing strong support for the two-binding site mechanism. Maximum enzyme turnover via oxidation of cytochrome c bound at the high-affinity site increases from 2 to 860 s-1 as the ionic strength is increased from 0.010 to 0.20 M. Oxidation of yeast iso-1 ferrocytochrome c is faster in the 2:1 complexes of cytochrome c peroxidase compounds I and II in comparison to the 1:1 complexes. The oxidation rates in the 2:1 complex are macroscopic rate constants equal to the sum of the oxidation rates via both the high- and low-affinity sites. The maximum enzyme turnover via the 2:1 complex increases from 1100 to 2700 s-1 over the ionic strength range 0.010-0.070 M.
Collapse
Affiliation(s)
- A L Matthis
- Department of Chemistry, Northern Illinois University, DeKalb 60115, USA
| | | |
Collapse
|
10
|
Kresheck GC, Vitello LB, Erman JE. Calorimetric studies on the interaction of horse ferricytochrome c and yeast cytochrome c peroxidase. Biochemistry 1995; 34:8398-405. [PMID: 7599130 DOI: 10.1021/bi00026a022] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The binding of horse ferricytochrome c to yeast cytochrome c peroxidase at pH 6.0 in 8.7 mM phosphate buffer (0.0100 M ionic strength) is characterized by a small, unfavorable enthalpy change (+1.91 +/- 0.16 kcal mol-1) and a large, positive entropy change (+37 +/- 1 eu). The free energy of binding depends strongly upon ionic strength, increasing from -9.01 to -4.51 kcal mol-1 between 0.0100 and 0.200 M ionic strength. The increase in free energy is due solely to the change in entropy over this ionic strength range, with the entropy change decreasing from 37 +/- 1 to 22 +/- 3 eu between 0.0100 and 0.200 M ionic strength. The observed enthalpy change remains constant over the same ionic strength range. At 0.0100 M ionic strength, complex formation is accompanied by the release of 0.54 +/- 0.11 proton, causing a variation in the observed enthalpy of reaction depending upon the buffer. After accounting for proton binding to the buffer, the corrected values for the enthalpy and entropy of binding are +2.84 +/- 0.26 kcal mol-1 and +21 +/- 3 eu, respectively. At 0.05 M ionic strength, the observed change in heat capacity, delta Cp, for the reaction between horse ferricytochrome c and cytochrome c peroxidase is essentially zero, 1.6 +/- 9.6 cal mol-1 K-1. The corrected delta Cp for binding is -28 +/- 10 cal mol-1 K-1 after accounting for proton binding to the buffer. No evidence for formation of a 2:1 horse ferricytochrome c/cytochrome c peroxidase complex was obtained in this study.
Collapse
Affiliation(s)
- G C Kresheck
- Department of Chemistry, Northern Illinois University, DeKalb 60115, USA
| | | | | |
Collapse
|
11
|
Su XD, Yonetani T, Skoglund U. The crystal structure of the iron-free cytochrome c peroxidase and its implication for the enzymatic mechanism. FEBS Lett 1994; 351:437-42. [PMID: 8082811 DOI: 10.1016/0014-5793(94)00910-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We report the refined structure of an iron-free form of cytochrome c peroxidase (CcP) at 2.3 A resolution. The backbone comparison between native CcP and iron-free CcP shows that the two structures have the same protein fold within experimental error. The only difference noted is in the heme pocket where the distance between the proximal histidine and the center of the protoporphyrin has increased. The results show that the iron-free CcP should be a good substitute for native CcP in fluorescence studies and thus also validate previous studies using iron-free CcPs as efficient fluorescent probes in electron transfer studies.
Collapse
Affiliation(s)
- X D Su
- Department of Cell and Molecular Biology, Medical Nobel Institute, Karolinska Institutet, Stockholm, Sweden
| | | | | |
Collapse
|
12
|
Jeng MF, Englander SW, Pardue K, Rogalskyj JS, McLendon G. Structural dynamics in an electron-transfer complex. NATURE STRUCTURAL BIOLOGY 1994; 1:234-8. [PMID: 7656052 DOI: 10.1038/nsb0494-234] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The dynamic behaviour of the complex of horse cytochrome c with cytochrome c peroxidase, an electron-transfer complex, was studied in solution by a hydrogen exchange labelling method together with two-dimensional NMR analysis. Although cytochrome c hydrogens in the expected binding region exhibit slowed exchange, the measured slowing factors are very small, indicating that hydrogen-exchange occurs with little hindrance from within the binding interface. The complex in solution must therefore be highly mobile rather than rigidly defined, as implied by the crystalline complex. This result is in conflict with the concept that biological electron transfer occurs by way of predetermined covalent pathways.
Collapse
Affiliation(s)
- M F Jeng
- Johnson Research Foundation, Department of Biochemistry & Biophysics, University of Pennsylvania School of Medicine, Philadelphia 19104-6059, USA
| | | | | | | | | |
Collapse
|
13
|
Reductions by ferrocytochrome c peroxidase 4. Kinetics of yeast cytochrome c reduction at high buffer phosphate concentration. Inorganica Chim Acta 1992. [DOI: 10.1016/s0020-1693(00)85339-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
|
14
|
Kim KL, Kang DS, Vitello LB, Erman JE. Cytochrome c peroxidase catalyzed oxidation of ferrocytochrome c by hydrogen peroxide: ionic strength dependence of the steady-state rate parameters. Biochemistry 1990; 29:9150-9. [PMID: 2176845 DOI: 10.1021/bi00491a008] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The steady-state kinetics of the cytochrome c peroxidase catalyzed oxidation of horse heart ferrocytochrome c by hydrogen peroxide have been studied at both pH 7.0 and pH 7.5 as a function of ionic strength. Plots of the initial velocity versus hydrogen peroxide concentration at fixed cytochrome c are hyperbolic. The limiting slope at low hydrogen peroxide give apparent bimolecular rate constants for the cytochrome c peroxidase-hydrogen peroxide reaction identical with those determined directly by stopped-flow techniques. Plots of the initial velocity versus cytochrome c concentration at saturating hydrogen peroxide (200 microM) are nonhyperbolic. The rate expression requires squared terms in cytochrome c concentration. The maximum turnover rate of the enzyme is independent of ionic strength, with values of 470 +/- 50 s-1 and 290 +/- 30 s-1 at pH 7.0 and 7.5, respectively. The limiting slope of velocity versus cytochrome c concentration plots provides a lower limit for the association rate constant between cytochrome c and the oxidized intermediates of cytochrome c peroxidase. The limiting slope varies from 10(6) M-1 s-1 at 300 mM ionic strength to 10(8) M-1 s-1 at 20 mM ionic strength and extrapolates to 5 x 10(8) M-1 s-1 at zero ionic strength. The data are discussed in terms of both a two-binding-site mechanism and a single-binding-site, multiple-pathway mechanism.
Collapse
Affiliation(s)
- K L Kim
- Department of Chemistry, Northern Illinois University, DeKalb 60115
| | | | | | | |
Collapse
|
15
|
Dixon DW, Hong X, Woehler SE. Electrostatic and steric control of electron self-exchange in cytochromes c, c551, and b5. Biophys J 1989; 56:339-51. [PMID: 2550090 PMCID: PMC1280483 DOI: 10.1016/s0006-3495(89)82680-3] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The ionic strength dependence of the electron self-exchange rate constants of cytochromes c, c551, and b5 has been analyzed in terms of a monopole-dipole formalism (van Leeuwen, J.W. 1983. Biochim. Biophys. Acta. 743:408-421). The dipole moments of the reduced and oxidized forms of Ps. aeruginosa cytochrome c551 are 190 and 210 D, respectively (calculated from the crystal structure). The projections of these on the vector from the center of mass through the exposed heme edge are 120 and 150 D. For cytochrome b5, the dipole moments calculated from the crystal structure are 500 and 460 D for the reduced and oxidized protein; the projections of these dipole moments through the exposed heme edge are -330 and -280 D. A fit of the ionic strength dependence of the electron self-exchange rate constants gives -280 (reduced) and -250 (oxidized) D for the center of mass to heme edge vector. The self-exchange rate constants extrapolated to infinite ionic strength of cytochrome c, c551, and b5 are 5.1 x 10(5), 2 x 10(7), and 3.7 x 10(5) M-1 s-1, respectively. The extension of the monopole-dipole approach to other cytochrome-cytochrome electron transfer reactions is discussed. The control of electron transfer by the size and shape of the protein is investigated using a model which accounts for the distance of the heme from each of the surface atoms of the protein. These calculations indicate that the difference between the electrostatically corrected self-exchange rate constants of cytochromes c and c551 is due only in part to the different sizes and heme exposures of the two proteins.
Collapse
Affiliation(s)
- D W Dixon
- Department of Chemistry, Georgia State University, Atlanta 30303
| | | | | |
Collapse
|
16
|
Electron transfer from cytochrome c to cytochrome c peroxidase across the bilayer lipid membrane (BLM). ACTA ACUST UNITED AC 1989. [DOI: 10.1016/0022-0728(89)87223-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
17
|
Summers FE, Erman JE. Reduction of cytochrome c peroxidase compounds I and II by ferrocytochrome c. A stopped-flow kinetic investigation. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)68216-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
18
|
Northrup SH, Boles JO, Reynolds JC. Brownian dynamics of cytochrome c and cytochrome c peroxidase association. Science 1988; 241:67-70. [PMID: 2838904 DOI: 10.1126/science.2838904] [Citation(s) in RCA: 257] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Brownian dynamics computer simulations of the diffusional association of electron transport proteins cytochrome c (cyt c) and cytochrome c peroxidase (cyt c per) were performed. A highly detailed and realistic model of the protein structures and their electrostatic interactions was used that was based on an atomic-level spatial description. Several structural features played a role in enhancing and optimizing the electron transfer efficiency of this reaction. Favorable electrostatic interactions facilitated long-lived nonspecific encounters between the proteins that allowed the severe orientational criteria for reaction to be overcome by rotational diffusion during encounters. Thus a "reduction-in-dimensionality" effect operated. The proteins achieved plausible electron transfer orientations in a multitude of electrostatically stable encounter complexes, rather than in a single dominant complex.
Collapse
Affiliation(s)
- S H Northrup
- Department of Chemistry, Tennessee Technological University, Cookeville 38505
| | | | | |
Collapse
|