@article {427,
	title = {Biochemical characterization of purified OmcS, a c-type cytochrome required for insoluble Fe(III) reduction in Geobacter sulfurreducens.},
	journal = {Biochim Biophys Acta},
	volume = {1807},
	year = {2011},
	month = {2011 Apr},
	pages = {404-12},
	abstract = {Previous studies with Geobacter sulfurreducens have demonstrated that OmcS, an abundant c-type cytochrome that is only loosely bound to the outer surface, plays an important role in electron transfer to Fe(III) oxides as well as other extracellular electron acceptors. In order to further investigate the function of OmcS, it was purified from a strain that overproduces the protein. Purified OmcS had a molecular mass of 47015 Da, and six low-spin bis-histidinyl hexacoordinated heme groups. Its midpoint redox potential was -212 mV. A thermal stability analysis showed that the cooperative melting of purified OmcS occurs in the range of 65-82 {\textdegree}C. Far UV circular dichroism spectroscopy indicated that the secondary structure of purified OmcS consists of about 10\% α-helix and abundant disordered structures. Dithionite-reduced OmcS was able to transfer electrons to a variety of substrates of environmental importance including insoluble Fe(III) oxide, Mn(IV) oxide and humic substances. Stopped flow analysis revealed that the reaction rate of OmcS oxidation has a hyperbolic dependence on the concentration of the studied substrates. A ten-fold faster reaction rate with anthraquinone-2,6-disulfonate (AQDS) (25.2 s$^{-}${\textonesuperior}) was observed as compared to that with Fe(III) citrate (2.9 s$^{-}${\textonesuperior}). The results, coupled with previous localization and gene deletion studies, suggest that OmcS is well-suited to play an important role in extracellular electron transfer.},
	keywords = {Circular Dichroism, Cytochrome c Group, Geobacter, Heme, Iron, Kinetics, Molecular Weight, Oxidation-Reduction, Solubility},
	issn = {0006-3002},
	doi = {10.1016/j.bbabio.2011.01.003},
	author = {Qian, Xinlei and Mester, T{\"u}nde and Morgado, Leonor and Arakawa, Tsutomu and Sharma, Manju L and Inoue, Kengo and Joseph, Crisjoe and Salgueiro, Carlos A and Maroney, Michael J and Lovley, Derek R}
}
@article {445,
	title = {Purification and characterization of OmcZ, an outer-surface, octaheme c-type cytochrome essential for optimal current production by Geobacter sulfurreducens.},
	journal = {Appl Environ Microbiol},
	volume = {76},
	year = {2010},
	month = {2010 Jun},
	pages = {3999-4007},
	abstract = {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 (thermal-denaturing temperature, 94.2 degrees 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.},
	keywords = {Binding Sites, Bioelectric Energy Sources, Cytochromes c, Electricity, Electron Transport, Geobacter, Heme, Hot Temperature, Molecular Sequence Data, Molecular Weight, Oxidation-Reduction, Protein Binding, Protein Stability, Sequence Alignment, Sequence Analysis, Protein},
	issn = {1098-5336},
	doi = {10.1128/AEM.00027-10},
	author = {Inoue, Kengo and Qian, Xinlei and Morgado, Leonor and Kim, Byoung-Chan and Mester, T{\"u}nde and Izallalen, Mounir and Salgueiro, Carlos A and Lovley, Derek R}
}
@article {496,
	title = {Evidence that OmcB and OmpB of Geobacter sulfurreducens are outer membrane surface proteins.},
	journal = {FEMS Microbiol Lett},
	volume = {277},
	year = {2007},
	month = {2007 Dec},
	pages = {21-7},
	abstract = {The c-type cytochrome (OmcB) and the multicopper protein (OmpB) required for Fe(III) oxide reduction by Geobacter sulfurreducens were predicted previously to be outer membrane proteins, but it is not clear whether they are positioned in a manner that permits the interaction with Fe(III). Treatment of whole cells with proteinase K inhibited Fe(III) reduction, but had no impact on the inner membrane-associated fumarate reduction. OmcB was digested by protease, resulting in a smaller peptide. However, immunogold labeling coupled with transmission electron microscopy did not detect OmcB, suggesting that it is only partially exposed on the cell surface. In contrast, OmpB was completely digested with protease. OmpB was loosely associated with the cell surface as a substantial portion of it was recovered in the culture supernatant. Immunogold labeling demonstrated that OmpB associated with the cell was evenly distributed on the cell surface rather than localized to one side of the cell like the conductive pili. Although several proteins required for Fe(III) oxide reduction are shown to be exposed on the outer surface of G. sulfurreducens, the finding that OmcB is also surface exposed is the first report of a protein required for optimal Fe(III) citrate reduction at least partially accessible on the cell surface.},
	keywords = {Bacterial Outer Membrane Proteins, Cell Membrane, Cytochromes c, Ferric Compounds, Geobacter, Microscopy, Electron, Transmission, Oxidation-Reduction, Peptide Hydrolases},
	issn = {0378-1097},
	doi = {10.1111/j.1574-6968.2007.00915.x},
	author = {Qian, Xinlei and Reguera, Gemma and Mester, T{\"u}nde and Lovley, Derek R}
}
@article {521,
	title = {Two putative c-type multiheme cytochromes required for the expression of OmcB, an outer membrane protein essential for optimal Fe(III) reduction in Geobacter sulfurreducens.},
	journal = {J Bacteriol},
	volume = {188},
	year = {2006},
	month = {2006 Apr},
	pages = {3138-42},
	abstract = {Deletion of two homologous Geobacter sulfurreducens c-type cytochrome genes, omcG and omcH, decreased the rate of Fe(III) reduction and decreased the level of an outer membrane cytochrome critical for Fe(III) reduction, OmcB, without affecting its transcription. Expression of either gene restored Fe(III) reduction and OmcB expression, suggesting functional similarity.},
	keywords = {Bacterial Outer Membrane Proteins, Bacterial Proteins, Blotting, Northern, Blotting, Western, Cytochromes c, Ferric Compounds, Gene Deletion, Gene Expression, Genes, Bacterial, Geobacter, Oxidation-Reduction, RNA, Bacterial, RNA, Messenger},
	issn = {0021-9193},
	doi = {10.1128/JB.188.8.3138-3142.2006},
	author = {Kim, Byoung-Chan and Qian, Xinlei and Leang, Ching and Coppi, Maddalena V and Lovley, Derek R}
}
