Involvement of the
            <i>Shewanella oneidensis</i>
            Decaheme Cytochrome MtrA in the Periplasmic Stability of the β-Barrel Protein MtrB

Schicklberger, Marcus; Bücking, Clemens; Schuetz, Bjoern; Heide, Heinrich; Gescher, Johannes

doi:10.1128/aem.01201-10

Cited by 38 publications

(40 citation statements)

References 23 publications

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“…It appears that MtrB plays a major role in the formation of a stable MtrCAB complex in the outer membrane, which is necessary for iron(III) reduction (25). Another study showed that MtrA is mislocalized in Shewanella strains lacking mtrB (7).…”

Section: Discussionmentioning

confidence: 99%

Characterization of Axial and Proximal Histidine Mutations of the Decaheme Cytochrome MtrA from Shewanella sp. Strain ANA-3 and Implications for the Electron Transport System

et al. 2012

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c Extracellular respiration of solid-phase electron acceptors in some microorganisms requires a complex chain of multiheme ctype cytochromes that span the inner and outer membranes. In Shewanella species, MtrA, an ϳ35-kDa periplasmic decaheme c-type cytochrome, is an essential component for extracellular respiration of iron(III). The exact mechanism of electron transport has not yet been resolved, but the arrangement of the polypeptide chain may have a strong influence on the capability of the MtrA cytochrome to transport electrons. The iron hemes of MtrA are bound to its polypeptide chain via proximal (CXXCH) and distal histidine residues. In this study, we show the effects of mutating histidine residues of MtrA to arginine on protein expression and extracellular respiration using Shewanella sp. strain ANA-3 as a model organism. Individual mutations to six out of nine proximal histidines in CXXCH of MtrA led to decreased protein expression. However, distal histidine mutations resulted in various degrees of protein expression. In addition, the effects of histidine mutations on extracellular respiration were tested using ferrihydrite and current production in microbial fuel cells. These results show that proximal histidine mutants were unable to reduce ferrihydrite. Mutations to the distal histidine residues resulted in various degrees of ferrihydrite reduction. These findings indicate that mutations to the proximal histidine residues affect MtrA expression, leading to loss of extracellular respiration ability. In contrast, mutations to the distal histidine residues are less detrimental to protein expression, and extracellular respiration can proceed.

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Section: Discussionmentioning

confidence: 99%

Characterization of Axial and Proximal Histidine Mutations of the Decaheme Cytochrome MtrA from Shewanella sp. Strain ANA-3 and Implications for the Electron Transport System

et al. 2012

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“…5). Both Hartshorne et al (7) and Schicklberger et al (30) found that correct expression of both MtrA and MtrB was required for their incorporation into the outer membrane of S. oneidensis. This unusual dependence suggests that MtrB does not insert into the membrane as a typical porin and that currently available predictive algorithms for porin topology may not predict the topology of porin-cytochrome complexes correctly.…”

Section: Discussionmentioning

confidence: 99%

Rapid electron exchange between surface-exposed bacterial cytochromes and Fe(III) minerals

White

Shi

et al. 2013

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

190

209

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The mineral-respiring bacterium Shewanella oneidensis uses a protein complex, MtrCAB, composed of two decaheme cytochromes, MtrC and MtrA, brought together inside a transmembrane porin, MtrB, to transport electrons across the outer membrane to a variety of mineral-based electron acceptors. A proteoliposome system containing a pool of internalized electron carriers was used to investigate how the topology of the MtrCAB complex relates to its ability to transport electrons across a lipid bilayer to externally located Fe(III) oxides. With MtrA facing the interior and MtrC exposed on the outer surface of the phospholipid bilayer, the established in vivo orientation, electron transfer from the interior electron carrier pool through MtrCAB to solid-phase Fe(III) oxides was demonstrated. The rates were 10 3 times higher than those reported for reduction of goethite, hematite, and lepidocrocite by S. oneidensis, and the order of the reaction rates was consistent with those observed in S. oneidensis cultures. In contrast, established rates for single turnover reactions between purified MtrC and Fe(III) oxides were 10 3 times lower. By providing a continuous flow of electrons, the proteoliposome experiments demonstrate that conduction through MtrCAB directly to Fe(III) oxides is sufficient to support in vivo, anaerobic, solid-phase iron respiration.mineral respiration | multiheme cytochromes | proteoliposome

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“…MtrA deletion mutants fail to correctly localize MtrB (30,80). Schicklberger et al showed recently that a lack of MtrA is connected to MtrB instability, which could be uncoupled by the deletion of the periplasmic protease DegP (80). However, the detailed mechanism of how the formation of the MtrABC complex is established and how MtrA could be involved in the stability of MtrB is unknown.…”

Section: Extracellular Electron Acceptorsmentioning

confidence: 99%

“…It is certainly involved in electron transfer but also in the assembly of the MtrABC complex. MtrA deletion mutants fail to correctly localize MtrB (30,80). Schicklberger et al showed recently that a lack of MtrA is connected to MtrB instability, which could be uncoupled by the deletion of the periplasmic protease DegP (80).…”

Section: Extracellular Electron Acceptorsmentioning

confidence: 99%

Dissimilatory Reduction of Extracellular Electron Acceptors in Anaerobic Respiration

Richter

Schicklberger

Gescher

2012

Appl Environ Microbiol

Self Cite

246

181

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An extension of the respiratory chain to the cell surface is necessary to reduce extracellular electron acceptors like ferric iron or manganese oxides. In the past few years, more and more compounds were revealed to be reduced at the surface of the outer membrane of Gram-negative bacteria, and the list does not seem to have an end so far. Shewanella as well as Geobacter strains are model organisms to discover the biochemistry that enables the dissimilatory reduction of extracellular electron acceptors. In both cases, c-type cytochromes are essential electron-transferring proteins. They make the journey of respiratory electrons from the cytoplasmic membrane through periplasm and over the outer membrane possible. Outer membrane cytochromes have the ability to catalyze the last step of the respiratory chains. Still, recent discoveries provided evidence that they are accompanied by further factors that allow or at least facilitate extracellular reduction. This review gives a condensed overview of our current knowledge of extracellular respiration, highlights recent discoveries, and discusses critically the influence of different strategies for terminal electron transfer reactions.

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Involvement of the Shewanella oneidensis Decaheme Cytochrome MtrA in the Periplasmic Stability of the β-Barrel Protein MtrB

Cited by 38 publications

References 23 publications

Characterization of Axial and Proximal Histidine Mutations of the Decaheme Cytochrome MtrA from Shewanella sp. Strain ANA-3 and Implications for the Electron Transport System

Characterization of Axial and Proximal Histidine Mutations of the Decaheme Cytochrome MtrA from Shewanella sp. Strain ANA-3 and Implications for the Electron Transport System

Rapid electron exchange between surface-exposed bacterial cytochromes and Fe(III) minerals

Dissimilatory Reduction of Extracellular Electron Acceptors in Anaerobic Respiration

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