Purification and characterization of OmcZ, an outer-surface, octaheme c-type cytochrome essential for optimal current production by Geobacter sulfurreducens.
Appl Environ Microbiol
; 76(12): 3999-4007, 2010 Jun.
Article
en En
| MEDLINE
| ID: mdl-20400562
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.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Fuentes de Energía Bioeléctrica
/
Geobacter
/
Citocromos c
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Electricidad
Idioma:
En
Revista:
Appl Environ Microbiol
Año:
2010
Tipo del documento:
Article
País de afiliación:
Estados Unidos