Outer membrane cytochrome c, OmcF, from Geobacter sulfurreducens: High structural similarity to an algal cytochrome c6

Pokkuluri, P.R.; Londer, Yuri Y.; Wood, Stephen; Duke, N.E.C.; Morgado, Leonor; Salgueiro, Carlos A.; Schiffer, M.

doi:10.1002/prot.22260

Cited by 32 publications

(42 citation statements)

References 24 publications

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“…However, only a few of them have been purified and characterized. They include PpcA, an abundant triheme periplasmic c-type cytochrome that plays an important role in Fe(III) reduction (28,38,43), as well as several monoheme cytochromes that may play a sensory role (22,44,45). None of the outer-surface c-type cytochromes has been purified to homogeneity.…”

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confidence: 99%

Purification and Characterization of OmcZ, an Outer-Surface, Octaheme c -Type Cytochrome Essential for Optimal Current Production by Geobacter sulfurreducens

Inoue

Qian

Morgado

et al. 2010

Appl Environ Microbiol

242

185

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Previous studies have demonstrated that Geobacter sulfurreducens requires the c-type cytochrome OmcZ, which is present in large (OmcZ L ; 50-kDa) and small (OmcZ S ; 30-kDa) forms, for optimal current production in microbial fuel cells. This protein was further characterized to aid in understanding its role in current production. Subcellular-localization studies suggested that OmcZ S was the predominant extracellular form of OmcZ. N-and C-terminal amino acid sequence analysis of purified OmcZ S and molecular weight measurements indicated that OmcZ S is a cleaved product of OmcZ L retaining all 8 hemes, including 1 heme with the unusual c-type heme-binding motif CX 14 CH. The purified OmcZ S was remarkably thermally stable (thermaldenaturing temperature, 94.2°C). Redox titration analysis revealed that the midpoint reduction potential of OmcZ S is approximately ؊220 mV (versus the standard hydrogen electrode [SHE]) with nonequivalent heme groups that cover a large reduction potential range (؊420 to ؊60 mV). OmcZ S transferred electrons in vitro to a diversity of potential extracellular electron acceptors, such as Fe(III) citrate, U(VI), Cr(VI), Au(III), Mn(IV) oxide, and the humic substance analogue anthraquinone-2,6-disulfonate, but not Fe(III) oxide. The biochemical properties and extracellular localization of OmcZ suggest that it is well suited for promoting electron transfer in current-producing biofilms of G. sulfurreducens.

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confidence: 99%

Purification and Characterization of OmcZ, an Outer-Surface, Octaheme c -Type Cytochrome Essential for Optimal Current Production by Geobacter sulfurreducens

Inoue

Qian

Morgado

et al. 2010

Appl Environ Microbiol

242

185

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“…The soluble part of OmcF (residues 20-104, hereafter referred to as OmcF S ) has sequence similarity to cytochromes c 6 of photosynthetic algae and cyanobacteria. These are acidic proteins with high reduction potentials of about ?350 mV at pH 7 (Pokkuluri et al 2009). On the contrary, OmcF S cytochrome is more basic (pI 7.8, as calculated with ExPASy Prot-Param, without the heme propionate groups) and has a much lower reduction potential (?180 mV at pH 7) (Pokkuluri et al 2009).…”

mentioning

confidence: 98%

“…These are acidic proteins with high reduction potentials of about ?350 mV at pH 7 (Pokkuluri et al 2009). On the contrary, OmcF S cytochrome is more basic (pI 7.8, as calculated with ExPASy Prot-Param, without the heme propionate groups) and has a much lower reduction potential (?180 mV at pH 7) (Pokkuluri et al 2009). In this work, 13 C, 15 N-labeled outer membrane cytochrome OmcF S was obtained and its solution structure determination by NMR is currently in progress.…”

mentioning

confidence: 98%

“…In addition to these observations, the outer membrane cytochrome OmcF (coded by gene gsu2432) is most likely a pivotal protein in the regulation of EET in Gs. In fact, gene knockout experiments showed that OmcF affects the Fe(III) citrate reduction, U(VI) reduction and the electrical current production by Gs in microbial fuel cells (Kim et al 2008;Pokkuluri et al 2009). However, the elucidation of the EET pathways in Gs is still in this infancy and no structural information in solution is available for any outer membrane cytochrome.…”

mentioning

confidence: 99%

“…However, the elucidation of the EET pathways in Gs is still in this infancy and no structural information in solution is available for any outer membrane cytochrome. The cytochrome OmcF contains 104 amino acids (11 kDa), including a predicted lipid anchor formed by the first 19 residues and one low-spin c-type heme group with axial His-Met coordination (Pokkuluri et al 2009). The soluble part of OmcF (residues 20-104, hereafter referred to as OmcF S ) has sequence similarity to cytochromes c 6 of photosynthetic algae and cyanobacteria.…”

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confidence: 99%

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Backbone, side chain and heme resonance assignments of cytochrome OmcF from Geobacter sulfurreducens

et al. 2015

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Gene knockout studies on Geobacter sulfurreducens (Gs) cells showed that the outer membrane cytochrome OmcF is involved in respiratory pathways leading to the extracellular reduction of Fe(III) citrate and U(VI) oxide. In addition, microarray analysis of OmcF-deficient mutant versus the wild-type strain revealed that many of the genes with decreased transcript level were those whose expression is upregulated in cells grown with a graphite electrode as electron acceptor. This suggests that OmcF also regulates the electron transfer to electrode surfaces and the concomitant electrical current production by Gs in microbial fuel cells. Extracellular electron transfer processes (EET) constitute nowadays the foundations to develop biotechnological applications in biofuel production, bioremediation and bioenergy. Therefore, the structural characterization of OmcF is a fundamental step to understand the mechanisms underlying EET. Here, we report the complete assignment of the heme proton signals together with (1)H, (13)C and (15)N backbone and side chain assignments of the OmcF, excluding the hydrophobic residues of the N-terminal predicted lipid anchor.

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Oxygenic Photosynthesis

Shevela¹,

Björn²

2013

Natural and Artificial Photosynthesis

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Outer membrane cytochrome c, OmcF, from Geobacter sulfurreducens: High structural similarity to an algal cytochrome c₆

Cited by 32 publications

References 24 publications

Purification and Characterization of OmcZ, an Outer-Surface, Octaheme c -Type Cytochrome Essential for Optimal Current Production by Geobacter sulfurreducens

Purification and Characterization of OmcZ, an Outer-Surface, Octaheme c -Type Cytochrome Essential for Optimal Current Production by Geobacter sulfurreducens

Backbone, side chain and heme resonance assignments of cytochrome OmcF from Geobacter sulfurreducens

Oxygenic Photosynthesis

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