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Direct electrochemistry of Shewanella oneidensis cytochrome c nitrite reductase: evidence of interactions across the dimeric interface.

Authors :
Judd ET
Youngblut M
Pacheco AA
Elliott SJ
Source :
Biochemistry [Biochemistry] 2012 Dec 21; Vol. 51 (51), pp. 10175-85. Date of Electronic Publication: 2012 Dec 12.
Publication Year :
2012

Abstract

Shewanella oneidensis cytochrome c nitrite reductase (soNrfA), a dimeric enzyme that houses five c-type hemes per protomer, conducts the six-electron reduction of nitrite and the two-electron reduction of hydroxylamine. Protein film voltammetry (PFV) has been used to study the cytochrome c nitrite reductase from Escherichia coli (ecNrfA) previously, revealing catalytic reduction of both nitrite and hydroxylamine substrates by ecNrfA adsorbed to a graphite electrode that is characterized by "boosts" and attenuations in activity depending on the applied potential. Here, we use PFV to investigate the catalytic properties of soNrfA during both nitrite and hydroxylamine turnover and compare those properties to the properties of ecNrfA. Distinct differences in both the electrochemical and kinetic characteristics of soNrfA are observed; e.g., all detected electron transfer steps are one-electron in nature, contrary to what has been observed in ecNrfA [Angove, H. C., Cole, J. A., Richardson, D. J., and Butt, J. N. (2002) J. Biol. Chem. 277, 23374-23381]. Additionally, we find evidence of substrate inhibition during nitrite turnover and negative cooperativity during hydroxylamine turnover, neither of which has previously been observed in any cytochrome c nitrite reductase. Collectively, these data provide evidence that during catalysis, potential pathways of communication exist between the individual soNrfA monomers comprising the native homodimer.

Details

Language :
English
ISSN :
1520-4995
Volume :
51
Issue :
51
Database :
MEDLINE
Journal :
Biochemistry
Publication Type :
Academic Journal
Accession number :
23210513
Full Text :
https://doi.org/10.1021/bi3011708