Distinct Electron Conductance Regimes in Bacterial Decaheme Cytochromes

Barrozo, Alexandre; El‐Naggar, Mohamed Y.; Krylov, Anna I.

doi:10.1002/ange.201800294

Cited by 10 publications

(16 citation statements)

References 35 publications

(109 reference statements)

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“…Electron flow from heme 10 or 5 to the side exits 7 and 2 is similarly fast as along the octaheme main chain, about 10 5 s −1 , except for 10 → 7 due to the relatively high reduction potential of heme 7. However, the latter is subject to uncertainty as discussed previously (26,27) and may be overestimated. The reverse flow from the side exit 7 or 2 to 10 and 5 is somewhat slower, typically about 10 4 s −1 , due to successive uphill steps involving coplanar and T-shaped motifs.…”

Section: Resultsmentioning

confidence: 93%

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Kinetics of trifurcated electron flow in the decaheme bacterial proteins MtrC and MtrF

Jiang

Burger

Gajdos

et al. 2019

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

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The bacterium Shewanella oneidensis has evolved a sophisticated electron transfer (ET) machinery to export electrons from the cytosol to extracellular space during extracellular respiration. At the heart of this process are decaheme proteins of the Mtr pathway, MtrC and MtrF, located at the external face of the outer bacterial membrane. Crystal structures have revealed that these proteins bind 10 c-type hemes arranged in the peculiar shape of a staggered cross that trifurcates the electron flow, presumably to reduce extracellular substrates while directing electrons to neighboring multiheme cytochromes at either side along the membrane. Especially intriguing is the design of the heme junctions trifurcating the electron flow: they are made of coplanar and T-shaped heme pair motifs with relatively large and seemingly unfavorable tunneling distances. Here, we use electronic structure calculations and molecular simulations to show that the side chains of the heme rings, in particular the cysteine linkages inserting in the space between coplanar and T-shaped heme pairs, strongly enhance electronic coupling in these two motifs. This results in an ≈103-fold speedup of ET steps at heme junctions that would otherwise be rate limiting. The predicted maximum electron flux through the solvated proteins is remarkably similar for all possible flow directions, suggesting that MtrC and MtrF shuttle electrons with similar efficiency and reversibly in directions parallel and orthogonal to the outer membrane. No major differences in the ET properties of MtrC and MtrF are found, implying that the different expression levels of the two proteins during extracellular respiration are not related to redox function.

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Section: Resultsmentioning

confidence: 93%

“…This undertaking is very timely, because the crystal structure of MtrC has recently become available. While Barrozo et al (27) have recently presented a preliminary characterization of the ET kinetics for MtrC, although with outdated electronic couplings from MtrF, a full and up-to-date characterization for this protein is outstanding.…”

mentioning

confidence: 99%

Kinetics of trifurcated electron flow in the decaheme bacterial proteins MtrC and MtrF

Jiang

Burger

Gajdos

et al. 2019

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

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“…In an early study, Breuer et al reported redox potentials for all 10 hemes in alloxidized MtrF using MD simulation, 25 and very recently Barrozo et al reported heme redox potentials for MtrF and MtrC in all-ox and all-red states. 31 Both studies agreed that the free energy profile for electron flow along the wire has ups and downs, yet resulting in near thermoneutral ET along the long axis of the protein (heme 5 to 10). In terms of kinetics, several ET mechanisms have been investigated including bandlike, 49 flickering resonance (FR), 28, 50 superexchange (SE) 28 and electron hopping.…”

Section: Electron Transfer Kineticsmentioning

confidence: 67%

“…These efforts may help us understand observed functional differences between the two proteins. 31 As always, computational predictions are subject to uncertainties (e.g. protonation state of the protein) and inaccuracies (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…Then I place focus on experimental measurements of electronic properties of single MHCs [22][23][24] and their complexes (nm length scale) 15 as well as their interpretation by theory and computation. [24][25][26][27][28][29][30][31] In this respect I distinguish between electron transfer (ET) and electron transport (ETp) measurements. In ET an electron transfers between an electron donor and an electron acceptor resulting in a change of their net charge, which is accompanied by dielectric relaxation of the environment if present.…”

Section: Introductionmentioning

confidence: 99%

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Electron transfer and transport through multi-heme proteins: recent progress and future directions

Blumberger

2018

Current Opinion in Chemical Biology

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I review recent experimental measurements probing electron transfer (ET) and electron transport (ETp) through multi-heme cytochromes (MHCs) as well as their theoretical interpretation. Examples include pump-probe spectroscopy of Ru-labeled MHCs aimed at determining heme-heme ET rates in MHCs and the measurement of the I-V characteristics of MHCs in bioelectronic junctions. While the ET mechanism appears to be well established for MHCs in aqueous solution, the ETp mechanism in bioelectronic junctions such as STM remains elusive partly due to the complexities of the electrode-protein interface.

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Inhibition of Tumor Progression through the Coupling of Bacterial Respiration with Tumor Metabolism

Chen

Wang

et al. 2020

Angewandte Chemie

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By leveraging the ability of Shewanella oneidensis MR-1 (S.oneidensis MR-1) to anaerobically catabolize lactate through the transfer of electrons to metal minerals for respiration, al actate-fueled biohybrid (Bac@MnO 2)w as constructed by modifying manganese dioxide (MnO 2)n anoflowers on the S. oneidensis MR-1 surface.T he biohybrid Bac@MnO 2 uses decorated MnO 2 nanoflowers as electron receptor and the tumor metabolite lactate as electron donor to make ac omplete bacterial respiration pathway at the tumor sites,which results in the continuous catabolism of intercellular lactate.A dditionally,d ecorated MnO 2 nanoflowers can also catalyze the conversion of endogenous hydrogen peroxide (H 2 O 2)into generate oxygen (O 2), which could prevent lactate production by downregulating hypoxia-inducible factor-1a (HIF-1a)e xpression. As lactate playsacritical role in tumor development, the biohybrid Bac@MnO 2 could significantly inhibit tumor progression by coupling bacteria respiration with tumor metabolism.

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Distinct Electron Conductance Regimes in Bacterial Decaheme Cytochromes

Abstract: Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Cited by 10 publications

References 35 publications

Kinetics of trifurcated electron flow in the decaheme bacterial proteins MtrC and MtrF

Kinetics of trifurcated electron flow in the decaheme bacterial proteins MtrC and MtrF

Electron transfer and transport through multi-heme proteins: recent progress and future directions

Inhibition of Tumor Progression through the Coupling of Bacterial Respiration with Tumor Metabolism

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