Long-range electron transfer

Gray, Harry B.; Winkler, Jay R.

doi:10.1073/pnas.0408029102

Cited by 744 publications

(884 citation statements)

References 101 publications

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“…According to Marcus' semiclassical theory, the outstanding efficiency of these processes is based on the maximization of the superexchange coupling between donor and acceptor and the minimization of the reorganization energy, given the low driving forces found in most biological systems (4)(5)(6). Thus, with driving forces as low as 0.1 eV and distances larger than 10 Å, efficient long-range electron transfer is only possible if the nuclear reorganization energy of the reactants is below 1 eV (4, 7).…”

mentioning

confidence: 99%

Flexibility of the metal-binding region in apo-cupredoxins

Zaballa

Abriata

Donaire

et al. 2012

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

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Protein-mediated electron transfer is an essential event in many biochemical processes. Efficient electron transfer requires the reorganization energy of the redox event to be minimized, which is ensured by the presence of rigid donor and acceptor sites. Electron transfer copper sites are present in the ubiquitous cupredoxin fold, able to bind one or two copper ions. The low reorganization energy in these metal centers has been accounted for by assuming that the protein scaffold creates an entatic/rack-induced state, which gives rise to a rigid environment by means of a preformed metal chelating site. However, this notion is incompatible with the need for an exposed metal-binding site and protein-protein interactions enabling metallochaperone-mediated assembly of the copper site. Here we report an NMR study that reveals a high degree of structural heterogeneity in the metal-binding region of the nonmetallated Cu A -binding cupredoxin domain, arising from microsecond to second dynamics that are quenched upon metal binding. We also report similar dynamic features in apo-azurin, a paradigmatic blue copper protein, suggesting a general behavior. These findings reveal that the entatic/rack-induced state, governing the features of the metal center in the copper-loaded protein, does not require a preformed metal-binding site. Instead, metal binding is a major contributor to the rigidity of electron transfer copper centers. These results reconcile the seemingly contradictory requirements of a rigid, occluded center for electron transfer, and an accessible, dynamic site required for in vivo copper uptake.metalloproteins | nuclear magnetic resonance | protein dynamics

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mentioning

confidence: 99%

Flexibility of the metal-binding region in apo-cupredoxins

Zaballa

Abriata

Donaire

et al. 2012

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

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“…T he flow of energy and information in natural systems is governed by carefully positioned donor and acceptor molecules 1 . The electrons flow through bond, through space or via a hopping mechanism.…”

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confidence: 99%

Photoinitiated charge separation in a hybrid titanium dioxide metalloporphyrin peptide material

et al. 2014

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In natural systems, electron flow is mediated by proteins that spatially organize donor and acceptor molecules with great precision. Achieving this guided, directional flow of information is a desirable feature in photovoltaic media. Here, we design self-assembled peptide materials that organize multiple electronic components capable of performing photoinduced charge separation. Two peptides, c16-AHL 3 K 3 -CO 2 H and c16-AHL 3 K 9 -CO 2 H, self-assemble into fibres and provide a scaffold capable of binding a metalloporphyrin via histidine axial ligation and mineralize titanium dioxide (TiO 2 ) on the lysine-rich surface of the resulting fibrous structures. Electron paramagnetic resonance studies of this self-assembled material under continuous light excitation demonstrate charge separation induced by excitation of the metalloporphyrin and mediated by the peptide assembly structure. This approach to dye-sensitized semiconducting materials offers a means to spatially control the dye molecule with respect to the semiconducting material through careful, strategic peptide design.

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“…The caging of uranium by these carboxyl ligands also positions the metal atom close to the most exposed tyrosine (Y57), which is predicted to catalyse the last step in electron transfer to extracellular electron acceptors (Feliciano et al ., 2015). The spatial distance between the caged metal and the tyrosine is less than 2 nm, a distance optimal for tunnelling (Gray and Winkler, 2005). The proximity of the carboxyl ligands to the tyrosine also favours its deprotonation, which could reduce the oxidation potential of the aromatic side‐chain to promote fast rates of electron transfer to the pilus‐bound metal via a proton‐coupled hopping mechanism (Stubbe et al ., 2003; Reece and Nocera, 2009).…”

Section: Geobacter T4p: a Paradigm In Structure And Functionmentioning

confidence: 99%

Harnessing the power of microbial nanowires

Reguera

2018

Microbial Biotechnology

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SummaryThe reduction of iron oxide minerals and uranium in model metal reducers in the genus Geobacter is mediated by conductive pili composed primarily of a structurally divergent pilin peptide that is otherwise recognized, processed and assembled in the inner membrane by a conserved Type IVa pilus apparatus. Electronic coupling among the peptides is promoted upon assembly, allowing the discharge of respiratory electrons at rates that greatly exceed the rates of cellular respiration. Harnessing the unique properties of these conductive appendages and their peptide building blocks in metal bioremediation will require understanding of how the pilins assemble to form a protein nanowire with specialized sites for metal immobilization. Also important are insights into how cells assemble the pili to make an electroactive matrix and grow on electrodes as biofilms that harvest electrical currents from the oxidation of waste organic substrates. Genetic engineering shows promise to modulate the properties of the peptide building blocks, protein nanowires and current‐harvesting biofilms for various applications. This minireview discusses what is known about the pilus material properties and reactions they catalyse and how this information can be harnessed in nanotechnology, bioremediation and bioenergy applications.

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Long-range electron transfer

Cited by 744 publications

References 101 publications

Flexibility of the metal-binding region in apo-cupredoxins

Flexibility of the metal-binding region in apo-cupredoxins

Photoinitiated charge separation in a hybrid titanium dioxide metalloporphyrin peptide material

Harnessing the power of microbial nanowires

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