Effects of Mutations in Plastocyanin on the Kinetics of the Protein Rearrangement Gating the Electron-Transfer Reaction with Zinc Cytochrome <i>c</i>. Analysis of the Rearrangement Pathway

Crnogorac, Milan M.; Shen, Chengyu; Young, Stanley; Hansson, Örjan; Kostić, Nenad M.

doi:10.1021/bi961914u

Cited by 48 publications

(70 citation statements)

References 77 publications

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“…In this limiting mechanism, the effective rate constant, k eff , is also proposed to become independent of R e (Eq. 2) and dependent on η (13,14,18,26,55). A number of examples of rigorously confirmed conformationally gated ET have been reported (13) and it appears to be of considerable biological importance.…”

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confidence: 93%

Fundamental signatures of short- and long-range electron transfer for the blue copper protein azurin at Au/SAM junctions

Khoshtariya

Dolidze

Shushanyan

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

126

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The blue copper protein from Pseudomonas aeruginosa, azurin, immobilized at gold electrodes through hydrophobic interaction with alkanethiol self-assembled monolayers (SAMs) of the general type [−S − ðCH 2 Þ n − CH 3 ] (n ¼ 4, 10, and 15) was employed to gain detailed insight into the physical mechanisms of short-and long-range biomolecular electron transfer (ET). Fast scan cyclic voltammetry and a Marcus equation analysis were used to determine unimolecular standard rate constants and reorganization free energies for variable n, temperature (2-55°C), and pressure (5-150 MPa) conditions. A novel global fitting procedure was found to account for the reduced ET rate constant over almost five orders of magnitude (covering different n, temperature, and pressure) and revealed that electron exchange is a direct ET process and not conformationally gated. All the ET data, addressing SAMs with thickness variable over ca. 12 Å, could be described by using a single reorganization energy (0.3 eV), however, the values for the enthalpies and volumes of activation were found to vary with n. These data and their comparison with theory show how to discriminate between the fundamental signatures of short-and long-range biomolecular ET that are theoretically anticipated for the adiabatic and nonadiabatic ET mechanisms, respectively. electron transfer mechanism | pressure | protein friction | reorganization | temperature T he intrinsic electron transfer (ET) mechanisms of even small and otherwise well-characterized proteins such as cytochrome c or azurin (Az) are difficult to identify conclusively because of the proteins' complexity, i.e., inhomogeneous structural and dynamic properties (1-14). The use of bioelectrochemical tunneling junctions, such as self-assembled monolayer (SAM) films of variable composition and thickness on metal electrodes, with redox proteins immobilized at the solution interface (or freely diffusing to the SAM terminal groups) have been shown to provide an assembly with well-defined and variable control parameters. As such, these assemblies are well suited for fundamental studies (15-32) and offer promise for versatile nanotechnology applications (32,33). On the basis of earlier fundamental efforts, this work studies ET between a Au electrode that is coated with a SAM alkanethiol film of variable thickness and a "model" biomolecular target, the blue copper protein, Az, from Pseudomonas aeruginosa that is immobilized through hydrophobic interactions onto the SAM. As a decisive development of the preceding work (19,20,25,26), we offer unique kinetic data obtained through temperature-and pressure-variation and the mechanistic analysis through a unique global fitting procedure accounting for ET at different SAM thickness, temperature, and pressure conditions that provided the variation of the reduced ET rate constant over almost five orders of magnitude. Importantly, our previous work demonstrated that Au-deposited SAMs can withstand pressure-related stress within 5 to 150 MPa (27, 28, 34).The rate constant, k ...

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confidence: 93%

Fundamental signatures of short- and long-range electron transfer for the blue copper protein azurin at Au/SAM junctions

Khoshtariya

Dolidze

Shushanyan

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

126

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“…[4][5][6] However, even for small and well-characterized proteins such as cytochrome c (CytC), [7,8] an intrinsic CT mechanism in "homogeneous" systems is difficult to recognize conclusively as a consequence of the extra structural and dynamic environmental complexity introduced by the participating redox partner. [4,5,[9][10][11] The covalent attachment of "small" complex ions as the redox counterparts at different external sites of CytC [12,13] does not warrant sufficiently smooth variation of intrinsic parameters, such as an electronic coupling (correlated with the CT distance; see below), because of the highly inhomogeneous nature of the protein interior. In this context, artificial bioelectrochemical devices made of electrode-deposited self-assembled monolayer (SAM) films of variable composition and thickness, and CytC or other redox proteins attached or freely diffusing to the SAM terminal groups (also subject to wide variations), were proven to be systems with wellcontrolled variable parameters, and hence suitable for fundamental studies [8,[14][15][16][17][18] and some technological applications.…”

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confidence: 99%

“…[18] Somewhat larger slopes were found for an ET within the "homogeneous" system involving zinc-substituted CytC, and wild-type and mutant cupriplastocyanin, which ranged from 0.7 to 0.9. [9][10][11] Interestingly, full viscosity control (d % 1) has been observed for photoinduced CT from the artificial Rucoordinated polypeptide electron donor to ferri-CytC, [48] which occurs through the loosely bound (encounter) complex as opposed to the "preformed" (tight) complex involving the same reactants (d % 0.6); both patterns occur simultaneously. The latter findings closely match the whole pattern of CytC bioelectrochemical CT in both the tightly bound and freely diffusing (to Au-deposited SAMs comprising w-COOH and w-OH) regimes, respectively.…”

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High‐Pressure Probing of a Changeover in the Charge‐Transfer Mechanism for Intact Cytochrome c at Gold/Self‐Assembled Monolayer Junctions

et al. 2005

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“…Very recently, computational simulation also indicates that the rearrangement is optimized through the -cation interaction between the phenol moiety of the remote electron transfer site Tyr 83 and the ⑀-amino group of lysine side chain of cytochrome f to the effective electron transfer interaction mode (21)(22)(23). Recent solution structure analysis of spinach plastocyanin indicates that the complex formation with cytochrome f dominantly occurs through the hydrophobic moiety of plastocyanin (24).…”

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confidence: 99%

The Structure and Unusual pH Dependence of Plastocyanin from the Fern Dryopteris crassirhizoma

Kohzuma¹,

Inoue²,

Yoshizaki³

et al. 1999

Journal of Biological Chemistry

114

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Spectroscopic properties, amino acid sequence, electron transfer kinetics, and crystal structures of the oxidized (at 1.7 Å resolution) and reduced form (at 1.8 Å resolution) of a novel plastocyanin from the fern Dryopteris crassirhizoma are presented. Kinetic studies show that the reduced form of Dryopteris plastocyanin remains redox-active at low pH, under conditions where the oxidation of the reduced form of other plastocyanins is inhibited by the protonation of a solvent-exposed active site residue, His 87 (equivalent to His 90 in Dryopteris plastocyanin). The x-ray crystal structure analysis of Dryopteris plastocyanin reveals -stacking between Phe 12 and His 90 , suggesting that the active site is uniquely protected against inactivation. Like higher plant plastocyanins, Dryopteris plastocyanin has an acidic patch, but this patch is located closer to the solvent-exposed active site His residue, and the total number of acidic residues is smaller. In the reactions of Dryopteris plastocyanin with inorganic redox reagents, the acidic patch (the "remote" site) and the hydrophobic patch surrounding His 90 (the "adjacent" site) are equally efficient for electron transfer. These results indicate the significance of the lack of protonation at the active site of Dryopteris plastocyanin, the equivalence of the two electron transfer sites in this protein, and a possibility of obtaining a novel insight into the photosynthetic electron transfer system of the first vascular plant fern, including its molecular evolutionary aspects. This is the first report on the characterization of plastocyanin and the first three-dimensional protein structure from fern plant.

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Effects of Mutations in Plastocyanin on the Kinetics of the Protein Rearrangement Gating the Electron-Transfer Reaction with Zinc Cytochrome c. Analysis of the Rearrangement Pathway

Cited by 48 publications

References 77 publications

Fundamental signatures of short- and long-range electron transfer for the blue copper protein azurin at Au/SAM junctions

Fundamental signatures of short- and long-range electron transfer for the blue copper protein azurin at Au/SAM junctions

High‐Pressure Probing of a Changeover in the Charge‐Transfer Mechanism for Intact Cytochrome c at Gold/Self‐Assembled Monolayer Junctions

The Structure and Unusual pH Dependence of Plastocyanin from the Fern Dryopteris crassirhizoma

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