Electron Transfer in Peptides with Cysteine and Methionine as Relay Amino Acids

Wang, Min; Gao, Jian; Müller, Pavel; Giese, Bernd

doi:10.1002/anie.200900827

Cited by 102 publications

(112 citation statements)

References 21 publications

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“…8−10 Methionine on the other hand can only serve as a hole stepping stone if the oxidized sulfur lone pair is stabilized by a nearby aromatic or amide moiety. 11−14 It was also shown that, even in the absence of the above-mentioned side groups, the backbones of α-and 3 10 -helices or β-turns can serve as relay stations. In the case of these structures, a large dipole moment decreases the oxidation potential especially at the C-termini of such structures.…”

Section: ■ Introductionmentioning

confidence: 99%

Electronic Structure of Hole-Conducting States in Polyprolines

2015

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Electron transfer over long distances in proteins by a hopping process requires transient relay stations that can harbor charge and spin for a short time span. Certain easily oxidizable or reducible side chains may assume that role, but it has been shown that charge transport in peptides can also take place in the absence of such groups which implies that the peptide backbone provides for hopping stations. We have identified three different types of radical cation states in such peptides that are associated with significantly lower ionization potentials than those of the constituent amino acids, and which may thus serve as relay stations for hole transport. Which of these states is the most stable one depends on the nature and the conformation of the peptide. In contrast to α-helices which, due to their high dipole moments, can only form stable radical cation states that are localized on the C-terminal amino acids, polyprolines are capable of accommodating such states inside the PPII helices and those states may serve as relay stations for hole transfer through polyprolines. Of which type these states are depends often on small conformational changes, and sometimes the most stable states are hybrids of the three types we have identified. ■ INTRODUCTIONThe transport of positive or negative charges over long distances is an essential function in living organisms. 1−3 For distances greater than ca. 2 nm, electron transfer in proteins can only occur in a multistep hopping process via "stepping stones" that are transiently oxidized or reduced during the process. 4,5 These relay stations allow one long and therefore very slow single step electron transfer to be divided into several short but quick steps which make that the rate of the electron transfer via multistep hopping decreases only slightly with the total distance between the electron donor and acceptor. 6,7 Several protein side groups were shown to be able to act as stepping stones in the course of hole transfer in proteins. They can be divided into two groups, the aromatic moieties in tyrosine, tryptophan, and imidazole, and the sulfur containing side chains in cysteine or methionine. The efficiency of the first group to serve as stepping stones is due to their low oxidation or reduction potentials, respectively. 8−10 Methionine on the other hand can only serve as a hole stepping stone if the oxidized sulfur lone pair is stabilized by a nearby aromatic or amide moiety. 11−14 It was also shown that, even in the absence of the above-mentioned side groups, the backbones of α-and 3 10 -helices or β-turns can serve as relay stations. In the case of these structures, a large dipole moment decreases the oxidation potential especially at the C-termini of such structures. 6,15−17 Another secondary structure is the so-called PPII helix which is found in most peptides including electron transport proteins like cytochrome C551 of Pseudomonas aeruginosa or bacteriochlorophyll A in the photosynthetic bacterium Prosthecochloris aestuarii. 18 A major component of...

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Section: ■ Introductionmentioning

confidence: 99%

Electronic Structure of Hole-Conducting States in Polyprolines

2015

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“…[5] The electron acceptor is generated by a laser flash of a precursor, which yields the aromatic radical cation (2→5, Scheme 1). [7] transferred from the peptide radical cation 14 to trimethoxyphenylalanine (8). The equilibrium constant is 0.25 (Scheme 3) and therefore 6 times smaller than the equilibrium constant of 1.5 (Scheme 2) using the amino acid radical cation 9 instead of the peptide 14.…”

Section: Relay Amino Acidsmentioning

confidence: 96%

“…1, 6→7). [8,10] A phenyl group can also stabilize a methionine radical cation by a neighbor group effect. [11] Our experiments with alkoxyphenylalanines indicate that in peptides also an aryl radical cation can be stabilized.…”

Section: Neighbor Group Effectsmentioning

confidence: 99%

“…Obviously, the aromatic radical cations in this peptide interact with the peptide. We have quantified this interaction in equilibration experiments with trimethoyxyphenylalanine (8). From equimolar amounts of peptide 15 and amino acid 8 we generated in a laser flash small amounts of the radical cations and measured an equilibrium of 14:10 = 80:20 (Scheme 3).…”

Section: Neighbor Group Effectsmentioning

confidence: 99%

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The Search for Relay Stations. Long-distance Electron Transfer in Peptides

Giese

Kracht

Cordes

2013

Chimia

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“…It is also of utmost importance that mechanisms of electron transfer through MNWs should be studied in MNWs produced by diverse micro-organisms (other than G. sulfurreducens and S. oneidensis). Apart from aromatic amino acids, sulfur-containing amino acids (methionine and cysteine) are also known to act as a relay in electron transfer (Sun et al, 2015;Wang et al, 2009). The probable role of these sulfur-containing amino acids (if present) in electron transfer through MNWs has not been studied so far and any involvement of these amino acids in conductivity of MNWs needs to be explored.…”

Section: Gaps In Current Research and Future Directionsmentioning

confidence: 99%

Microbial nanowires: an electrifying tale

et al. 2016

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Electromicrobiology has gained momentum in the last 10 years with advances in microbial fuel cells and the discovery of microbial nanowires (MNWs). The list of MNW-producing micro-organisms is growing and providing intriguing insights into the presence of such micro-organisms in diverse environments and the potential roles MNWs can perform. This review discusses the MNWs produced by different micro-organisms, including their structure, composition and mechanism of electron transfer through MNWs. Two hypotheses, metalliclike conductivity and an electron hopping model, have been proposed for electron transfer and we present a current understanding of both these hypotheses. MNWs not only are poised to change the way we see micro-organisms but also may impact the fields of bioenergy, biogeochemistry and bioremediation; hence, their potential applications in these fields are highlighted here.

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Electron Transfer in Peptides with Cysteine and Methionine as Relay Amino Acids

Abstract: Caught on the hop: In multistep electron transfer (ET) reactions through peptides, aliphatic amino acids can also act as relay stations. With cysteine, the reaction occurs as a proton-coupled electron transfer (PCET) with water used as a mediator for the proton transfer (see picture).

Cited by 102 publications

References 21 publications

Electronic Structure of Hole-Conducting States in Polyprolines

Electronic Structure of Hole-Conducting States in Polyprolines

The Search for Relay Stations. Long-distance Electron Transfer in Peptides

Microbial nanowires: an electrifying tale

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