title: Purification and characterization of OmcZ, an outer-surface, octaheme c-type cytochrome essential for optimal current production by Geobacter sulfurreducens.
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.
authors.affiliation: Department of Microbiology, University of Massachusetts, 639 North Pleasant St., Amherst, MA 01003, USA. kinoue@microbio.umass.edu
authors.forename: Kengo
authors.initials: K
authors.lastname: Inoue
authors.forename: Xinlei
authors.initials: X
authors.lastname: Qian
authors.forename: Leonor
authors.initials: L
authors.lastname: Morgado
authors.forename: Byoung-Chan
authors.initials: BC
authors.lastname: Kim
authors.forename: Tünde
authors.initials: T
authors.lastname: Mester
authors.forename: Mounir
authors.initials: M
authors.lastname: Izallalen
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Salgueiro
authors.forename: Derek R
authors.initials: DR
authors.lastname: Lovley
mesh_terms: D001665:Binding Sites; D001674:Bioelectric Energy Sources; D045304:Cytochromes c / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D004560:Electricity; D004579:Electron Transport; D045302:Geobacter / Q000201:enzymology* / Q000378:metabolism*; D006418:Heme / Q000378:metabolism; D006358:Hot Temperature; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010084:Oxidation-Reduction; D011485:Protein Binding; D055550:Protein Stability; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein
chemical_list: D006418:Heme; D045304:Cytochromes c
references.citation: Annu Rev Microbiol. 1993;47:263-90
references.pmid: 8257100
references.citation: J Bacteriol. 2007 Nov;189(21):7634-42
references.pmid: 17766415
references.citation: Anal Biochem. 1976 May 7;72:248-54
references.pmid: 942051
references.citation: Environ Microbiol. 2008 Oct;10(10):2505-14
references.pmid: 18564184
references.citation: FEMS Microbiol Lett. 2000 Apr 15;185(2):205-11
references.pmid: 10754249
references.citation: Biosens Bioelectron. 2009 Aug 15;24(12):3498-503
references.pmid: 19487117
references.citation: BMC Microbiol. 2007 Mar 08;7:16
references.pmid: 17346345
references.citation: PLoS One. 2009 May 20;4(5):e5628
references.pmid: 19461962
references.citation: Microbiology (Reading). 2007 Oct;153(Pt 10):3572-3585
references.pmid: 17906154
references.citation: Science. 2002 Jan 18;295(5554):483-5
references.pmid: 11799240
references.citation: Biochim Biophys Acta. 2008 Sep;1777(9):1157-65
references.pmid: 18534185
references.citation: Biochim Biophys Acta. 2007 Sep;1767(9):1169-79
references.pmid: 17692816
references.citation: Biochem J. 2001 Oct 1;359(Pt 1):147-52
references.pmid: 11563978
references.citation: PLoS Biol. 2006 Sep;4(9):e268
references.pmid: 16875436
references.citation: Curr Opin Cell Biol. 2000 Aug;12(4):420-30
references.pmid: 10873830
references.citation: Environ Microbiol Rep. 2009 Aug;1(4):220-7
references.pmid: 23765850
references.citation: Biochem Soc Trans. 2006 Feb;34(Pt 1):146-9
references.pmid: 16417506
references.citation: Mol Microbiol. 2007 May;64(4):1049-60
references.pmid: 17501927
references.citation: Appl Microbiol Biotechnol. 2007 Nov;77(2):393-402
references.pmid: 17786426
references.citation: Appl Environ Microbiol. 2003 Mar;69(3):1548-55
references.pmid: 12620842
references.citation: Arch Microbiol. 1993;159(4):336-44
references.pmid: 8387263
references.citation: J Bacteriol. 2005 Jul;187(13):4505-13
references.pmid: 15968061
references.citation: J Biol Inorg Chem. 2007 Sep;12(7):1083-94
references.pmid: 17701062
references.citation: J Bacteriol. 2003 Apr;185(7):2096-103
references.pmid: 12644478
references.citation: Appl Environ Microbiol. 2008 Dec;74(23):7348-55
references.pmid: 18836002
references.citation: Biochemistry. 2006 Nov 21;45(46):13910-7
references.pmid: 17105209
references.citation: Microb Ecol. 2004 Aug;48(2):178-90
references.pmid: 15546038
references.citation: Biosens Bioelectron. 2008 Dec 1;24(4):1012-7
references.pmid: 18804995
references.citation: Microbiol Mol Biol Rev. 2009 Sep;73(3):510-28, Table of Contents
references.pmid: 19721088
references.citation: Chembiochem. 2001 Nov 5;2(11):831-7
references.pmid: 11948869
references.citation: Biochem J. 2003 Jan 1;369(Pt 1):153-61
references.pmid: 12356333
references.citation: Biochim Biophys Acta. 2006 Jul;1764(7):1198-206
references.pmid: 16797259
references.citation: Protein Eng. 1992 Apr;5(3):191-5
references.pmid: 1409538
references.citation: Mol Microbiol. 2007 Jul;65(1):12-20
references.pmid: 17581116
references.citation: Appl Environ Microbiol. 1994 Oct;60(10):3752-9
references.pmid: 7527204
references.citation: Anal Biochem. 1984 Feb;136(2):509-14
references.pmid: 6202169
references.citation: Water Res. 2008 Mar;42(6-7):1501-10
references.pmid: 18035391
references.citation: Methods Enzymol. 1994;235:225-34
references.pmid: 8057896
references.citation: Anal Biochem. 1976 Sep;75(1):168-76
references.pmid: 822747
references.citation: Appl Environ Microbiol. 2010 Apr;76(7):2371-5
references.pmid: 20154112
references.citation: J Bacteriol. 2005 Sep;187(17):5918-26
references.pmid: 16109933
references.citation: Appl Environ Microbiol. 2001 Jul;67(7):3180-7
references.pmid: 11425739
references.citation: Biochim Biophys Acta. 2008 Dec;1784(12):1935-41
references.pmid: 18638577
references.citation: Chembiochem. 2001 Dec 3;2(12):895-905
references.pmid: 11948878
references.citation: Anal Biochem. 1985 Oct;150(1):76-85
references.pmid: 3843705
references.citation: Anal Biochem. 1987 Feb 15;161(1):1-15
references.pmid: 3578775
references.citation: Appl Microbiol Biotechnol. 2005 Feb;66(5):475-85
references.pmid: 15630515
references.citation: Nat Biotechnol. 2002 Aug;20(8):821-5
references.pmid: 12091916
references.citation: J Bacteriol. 2001 Aug;183(15):4468-76
references.pmid: 11443080
references.citation: Appl Environ Microbiol. 2005 Dec;71(12):8634-41
references.pmid: 16332857
references.citation: Proteins. 2009 Jan;74(1):266-70
references.pmid: 18837462
references.citation: J Mol Biol. 2008 Apr 11;377(5):1498-517
references.pmid: 18329666
references.citation: Environ Microbiol. 2008 Feb;10(2):497-505
references.pmid: 18093163