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Title 

Purification and characterization of OmcZ, an outer-surface, octaheme c-type cytochrome essential for optimal current production by Geobacter sulfurreducens

Authors 

K InoueX QianL MorgadoByoung Chan KimM IzallalenC A SalgueiroD R Lovley

Publisher 

American Society for Microbiology

Issue Date 

2010

Citation 

Applied and Environmental Microbiology, vol. 76, no. 12, pp. 3999-4007

Keywords 

Amino acid sequenceBiochemical propertiesC-type cytochromeCurrent productionElectron acceptorElectron transferExtracellularGeobacter sulfurreducensHeme bindingHeme groupHumic substancesIn-vitroMolecular weight measurementsOptimal currentRedox titrationsReduction potentialStandard hydrogen electrodesSub-cellularSulfurreducensThermally stable

Abstract 

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 (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). 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.

ISSN 

0099-2240

Link 

http://dx.doi.org/10.1128/AEM.00027-10

Appears in Collections

1. Journal Articles > Journal Articles

Registered Date

2019-05-02


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