@article {6236,
	title = {Purification and Characterization of OmcZ, an Outer-Surface, Octaheme c-Type Cytochrome Essential for Optimal Current Production by Geobacter sulfurreducens},
	journal = {Applied and Environmental Microbiology},
	volume = {76},
	year = {2010},
	pages = {3999-4007},
	abstract = {<p>Previous studies have demonstrated that Geobacter sulfurreducens requires the c-type cytochrome OmcZ, which is present in large (OmcZL; 50-kDa) and small (OmcZS; 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 OmcZS was the predominant extracellular form of OmcZ. N- and C-terminal amino acid sequence analysis of purified OmcZS and molecular weight measurements indicated that OmcZS is a cleaved product of OmcZL retaining all 8 hemes, including 1 heme with the unusual c-type heme-binding motif CX14CH. The purified OmcZS was remarkably thermally stable (thermal-denaturing temperature, 94.2{\textdegree}C). Redox titration analysis revealed that the midpoint reduction potential of OmcZS 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). OmcZS 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.</p>
},
	url = {http://aem.asm.org/content/76/12/3999.long},
	author = {Inoue, Kengo and Qian, Xinlei and Leonor Morgado and Kim, Byoung-Chan and Mester, T{\"u}nde and Izallalen, Mounir and Salgueiro, , Carlos A. and Lovley, Derek R.}
}
