Electron-transfer self-exchange kinetics of cytochrome b5

Dixon, Dabney W.; Hong, Xiaole; Woehler, S. E.; Mauk, A. Grant; Sishta, Bhavini P.

doi:10.1021/ja00159a030

Cited by 58 publications

(73 citation statements)

References 2 publications

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“…They are similar to those obtained for the cytochrome c adsorbed on the same SAM [1,58,61] and result to be lower than those for freely diffusing cupredoxins [63][64][65]. A similar effect of protein immobilization on k has been found for cytochrome c [21,[60][61][62] for which the reorganization energy is remarkably affected by the nature of the SAM.…”

Section: Discussionsupporting

confidence: 84%

Thermodynamics and kinetics of the electron transfer process of spinach plastocyanin adsorbed on a modified gold electrode

Ranieri

Battistuzzi

Borsari

et al. 2009

Journal of Electroanalytical Chemistry

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Section: Discussionsupporting

confidence: 84%

Thermodynamics and kinetics of the electron transfer process of spinach plastocyanin adsorbed on a modified gold electrode

Ranieri

Battistuzzi

Borsari

et al. 2009

Journal of Electroanalytical Chemistry

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“…The calculated values for the inner-sphere reorganization energy lie between 16 and 37 kcal/mol, which is in good agreement with what was measured for the selfexchange reorganization energy of cytochrome c [90]. The calculated values suggest adiabatic barriers ranging from an effectively barrierless reaction (CH2 ?…”

Section: Kinetic Barrier Calculationsupporting

confidence: 86%

Reductive activation of the heme iron–nitrosyl intermediate in the reaction mechanism of cytochrome c nitrite reductase: a theoretical study

Bykov

Neese

2012

J Biol Inorg Chem

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Cytochrome c nitrite reductase catalyzes the six-electron, seven-proton reduction of nitrite to ammonia without release of any detectable reaction intermediate. This implies a unique flexibility of the active site combined with a finely tuned proton and electron delivery system. In the present work, we employed density functional theory to study the recharging of the active site with protons and electrons through the series of reaction intermediates based on nitrogen monoxide [Fe(II)-NO(+), Fe(II)-NO·, Fe(II)-NO(-), and Fe(II)-HNO]. The activation barriers for the various proton and electron transfer steps were estimated in the framework of Marcus theory. Using the barriers obtained, we simulated the kinetics of the reduction process. We found that the complex recharging process can be accomplished in two possible ways: either through two consecutive proton-coupled electron transfers (PCETs) or in the form of three consecutive elementary steps involving reduction, PCET, and protonation. Kinetic simulations revealed the recharging through two PCETs to be a means of overcoming the predicted deep energetic minimum that is calculated to occur at the stage of the Fe(II)-NO· intermediate. The radical transfer role for the active-site Tyr(218), as proposed in the literature, cannot be confirmed on the basis of our calculations. The role of the highly conserved calcium located in the direct proximity of the active site in proton delivery has also been studied. It was found to play an important role in the substrate conversion through the facilitation of the proton transfer steps.

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“…Given the absence of Coulombic repulsion the k ese of A. variabilis PCu can be considered to be representative of the maximum in vitro value attainable within this family. These results are consistent with previous ESE studies on redox metalloproteins (8,22,34,36,(47)(48)(49) (Table I). Hydrophobic interactions are favored at high I and the small k ese (and k inf ) for D. crassirhizoma PCu can be partly explained by the less hydrophobic binding site in this protein (Fig.…”

Section: Ionic Strength Dependence Of the Ese Rate Constant-thesupporting

confidence: 93%

Transient Homodimer Interactions Studied Using the Electron Self-exchange Reaction

Sato

Crowley

Dennison

2005

Journal of Biological Chemistry

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Protein-protein interactions are vital to cellular function and recent studies have revealed the complexity of protein interaction networks (1, 2). Considering the crowded environment of the cell, weak (transient) protein interactions are expected to be ubiquitous (3). However, given their low affinity, such complexes tend to be overlooked by high-throughput proteomics.The structural features of protein-protein interfaces that enable transient interactions are not well understood, although poor geometric complementarity seems to be a prerequisite (4 -7). The interfaces of electron transfer (ET) 1 protein complexes, which represent an extreme in terms of low affinity and specificity (5), have the poorest surface complementarity (6).Electron self-exchange (ESE) is a simple reaction exhibited by redox proteins that provides a measure of their ET capabilities. An essential step in ESE is homodimer formation giving rise to transient protein interactions on the submillisecond time scale. To investigate the features of transient proteinprotein interactions involved in ET we have studied the influence of ionic strength on the ESE reactivity of a single family of redox metalloproteins. For this purpose we have chosen the plastocyanins (PCus), which are cupredoxins involved in photosynthetic ET, as their surface features vary considerably depending upon the organism from which the protein is obtained, yet their active site structures are almost identical (8).Plastocyanin is one of the best structurally characterized ET metalloproteins and possesses a ␤-barrel structure with the type 1 copper ion buried ϳ6 Å beneath the protein surface (Fig. 1A) (9 -13). Higher plant PCus have two distinct surface features (9, 11), namely the hydrophobic patch surrounding the exposed His 87 ligand, and the acidic patch that is more distant from the copper site (Fig. 1). In the PCu from the fern Dryopteris crassirhizoma (seedless, vascular plant) the acidic region is relocated and surrounds the hydrophobic patch ( Fig. 1) (13). In green algal PCus the acidic patch is more diffuse (12), whereas in the cyanobacterial PCus it is non-existent ( Fig. 1) (10). The charged and hydrophobic patches of PCu are utilized in the interaction with both physiological ET partners; cytochrome f (cytochrome f of the cytochrome b 6 f complex) and photosystem I (PSI) (5,(15)(16)(17)(18)(19)(20)(21). It has been shown that the structure of the interface between PCu and cytochrome f is organism-dependent (5, 19).Herein we study the influence of ionic strength (NaCl) on the ESE rate constants of spinach (higher plant), D. crassirhizoma, Ulva pertusa (green alga), and Anabaena variabilis (cyanobacterium) PCus. We also investigate the influence of the physiologically relevant Mg 2ϩ ion and temperature on the ESE reactivity of spinach PCu, the most highly charged protein studied. Protein modeling and docking simulations have been used to obtain representative structures of the transient homodimers formed. These models highlight the features of the proteinprotein i...

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Electron-transfer self-exchange kinetics of cytochrome b5

Cited by 58 publications

References 2 publications

Thermodynamics and kinetics of the electron transfer process of spinach plastocyanin adsorbed on a modified gold electrode

Thermodynamics and kinetics of the electron transfer process of spinach plastocyanin adsorbed on a modified gold electrode

Reductive activation of the heme iron–nitrosyl intermediate in the reaction mechanism of cytochrome c nitrite reductase: a theoretical study

Transient Homodimer Interactions Studied Using the Electron Self-exchange Reaction

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