Long-Range Electron Transfer in Engineered Azurins Exhibits Marcus Inverted Region Behavior

Farver, Ole; Hosseinzadeh, Parisa; Marshall, Nicholas; Wherland, Scot; Lu, Yi; Pecht, Israel

doi:10.1021/jz5022685

Cited by 30 publications

(31 citation statements)

References 54 publications

(71 reference statements)

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“…This lowering of reorganization energy is attributed to an increase in flexibility of the copper site for these mutants [291]. By considering more variants in SCS using the guidelines provided by previous studies, [235] they showed experimental evidence of the Marcus inverted region in a non-derivatized protein system [292] (Figure 28). …”

Section: Case Studiesmentioning

confidence: 99%

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Design and fine-tuning redox potentials of metalloproteins involved in electron transfer in bioenergetics

Hosseinzadeh¹,

Lu²

2016

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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163

121

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Redox potentials are the major contributors to controlling the ET rates and thus regulating ET processes in the bioenergetics. To maximize the efficiency of the ET process, one needs to master the art of tuning of the E°, especially metalloproteins, as they represent major classes of ET proteins. In this review, we first describe the importance of tuning E° of ET centers, including the metalloproteins described above, and its role in regulating the ET in bioenergetic processes including photosynthesis and respiration. The major focus of this review is to summarize recent work in designing the ET centers, namely cupredoxins, cytochromes, and iron-sulfur proteins, and examples in design of protein networks involved these ET centers. We then discuss the factors that affect redox potentials of these ET centers including metal ion, the ligands to metal center and interactions beyond the primary ligand, especially non-covalent secondary coordination sphere interactions. We gave examples of strategies to fine-tune the redox potential using both natural and unnatural amino acids and native and nonnative cofactors. Several case studies are used to illustrate recent successes in this area. Outlooks for future endeavors are also provided.

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Section: Case Studiesmentioning

confidence: 99%

“…Plot of ET rate vs. driving force of intermolecular ET in several azurin mutants, Reprinted with permission from [292]. Copyright {2015} American Chemical Society.…”

Section: Figurementioning

confidence: 99%

Design and fine-tuning redox potentials of metalloproteins involved in electron transfer in bioenergetics

Hosseinzadeh¹,

Lu²

2016

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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163

121

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“…Scott et al [43] studied intramolecular ET in cytochrome b 5 labeled with Ruthenium(II) polypyridine complexes with different E m values. Farver et al [44] recently studied the intramolecular ET reactions between the copper of azurin a disulfide radical anion with several site-directed mutants that spanned a wide range of E m values. The ΔG°-dependence of the ET reaction between MADH and amicyanin had previously been examined by looking at the rates of the forward and reverse reactions of amicyanin with different redox forms of MADH [19, 21].…”

Section: Discussionmentioning

confidence: 99%

Characterization of the free energy dependence of an interprotein electron transfer reaction by variation of pH and site-directed mutagenesis

Dow¹,

Davidson²

2015

Biochimica et Biophysica Acta (BBA) - Bioenergetics

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The interprotein electron transfer (ET) reactions of the cupredoxin amicyanin, which mediates ET from the tryptophan tryptophylquinone (TTQ) cofactor of methylamine dehydrogenase to cytochrome c-551i have been extensively studied. However, it was not possible to perform certain key experiments in that native system. This study examines the ET reaction from reduced amicyanin to an alternative electron acceptor, the diheme protein MauG. It was possible to vary the ΔG° for this ET reaction by simply changing pH to determine the dependence of kET on ΔG°. A P94A mutation of amicyanin significantly altered its oxidation-reduction midpoint potential value. It was not possible to study the ET from reduced P94A amicyanin to cytochrome c-551i in the native system because that reaction was kinetically coupled. However, the reaction from reduced P94A amicyanin to MauG was a true ET reaction and it was possible to determine values of reorganization energy (λ) and electronic coupling for the reactions of this variant as well as WT amicyanin. Comparison of the λ values associated with the ET reactions between amicyanin and the TTQ of methylamine dehydrogenase, the diheme center of MauG and the single heme of cytochrome c-551i, provides insight into the factors that dictate the λ values for the respective reactions. These results demonstrate how study of ET reactions with alternative redox partner proteins can complement and enhance our understanding of the reactions with the natural redox partners, and further our understanding of mechanisms of protein ET reactions.

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“…λ values have also been determined for ET reactions between native redox cofactors and redox-active active tags such as Ruthenium complexes [30, 31]. ET reactions between the copper of azurin a disulfide radical anion were used to determine λ [32]. The proteins used in the present study are among the few for which λ values have been experimentally determined for the reactions with their natural redox partners; the reactions of amicyanin with MADH [33] and cytochrome c -551i [34], and the reactions between MauG and preMADH and MADH [11].…”

Section: Discussionmentioning

confidence: 99%

Converting the bis-FeIV state of the diheme enzyme MauG to Compound I decreases the reorganization energy for electron transfer

Dow

Davidson

2015

Biochemical Journal

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The electron transfer (ET) properties of two types of high-valent hemes were studied within the same protein matrix; the bis-FeIV state of MauG and the Compound I state of Y294H MauG. The latter is formed as a consequence of mutation of the Tyr which forms the distal axial ligand of the six-coordinate heme that allows it to stabilize FeIV in the absence of an external ligand. The rates of the ET reaction of each high-valent species with the type I copper protein, amicyanin, were determined at different temperatures and analyzed by ET theory. The reaction with bis-FeIV WT MauG exhibited a reorganization energy (λ) that was 0.39 eV greater than that for the reaction of Compound I Y295H MauG. It is concluded that the delocalization of charge over the two hemes in the bis-FeIV state is responsible for the larger λ, relative to the Compound I state in which the FeV equivalent is isolated on one heme. While the increase in λ decreases the rate of ET, the delocalization of charge decreases the ET distance in its natural substrate protein, thus increasing the ET rate. This describes how proteins can balance different ET properties of complex redox cofactors to optimize each system for its particular ET or catalytic reaction.

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Long-Range Electron Transfer in Engineered Azurins Exhibits Marcus Inverted Region Behavior

Cited by 30 publications

References 54 publications

Design and fine-tuning redox potentials of metalloproteins involved in electron transfer in bioenergetics

Design and fine-tuning redox potentials of metalloproteins involved in electron transfer in bioenergetics

Characterization of the free energy dependence of an interprotein electron transfer reaction by variation of pH and site-directed mutagenesis

Converting the bis-FeIV state of the diheme enzyme MauG to Compound I decreases the reorganization energy for electron transfer

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