The denitrifying bacterium Paracoccus denitrificans can grow aerobically or anaerobically using nitrate or nitrite as the sole nitrogen source. The biochemical pathway responsible is expressed from a gene cluster comprising a nitrate/nitrite transporter (NasA), nitrite transporter (NasH), nitrite reductase (NasB), ferredoxin (NasG) and nitrate reductase (NasC). NasB and NasG are essential for growth with nitrate or nitrite as the nitrogen source. NADH serves as the electron donor for nitrate and nitrite reduction, but only NasB has a NADH-oxidizing domain. Nitrate and nitrite reductase activities show the same Km for NADH and can be separated by anion-exchange chromatography, but only fractions containing NasB retain the ability to oxidize NADH. This implies that NasG mediates electron flux from the NADH-oxidizing site in NasB to the sites of nitrate and nitrite reduction in NasC and NasB respectively. Delivery of extracellular nitrate to NasBGC is mediated by NasA, but both NasA and NasH contribute to nitrite uptake. The roles of NasA and NasC can be substituted during anaerobic growth by the biochemically distinct membrane-bound respiratory nitrate reductase (Nar), demonstrating functional overlap. nasG is highly conserved in nitrate/nitrite assimilation gene clusters, which is consistent with a key role for the NasG ferredoxin, as part of a phylogenetically widespread composite nitrate and nitrite reductase system.
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May 2011
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Research Article|
April 13 2011
A composite biochemical system for bacterial nitrate and nitrite assimilation as exemplified by Paracoccus denitrificans
Andrew J. Gates;
Andrew J. Gates
1
*Centre for Molecular and Structural Biochemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, U.K.
†School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, U.K.
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Victor M. Luque-Almagro;
Victor M. Luque-Almagro
1
‡Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, Edificio Severo Ochoa, 1 planta, Campus de Rabanales, Córdoba 14071, Spain
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Alan D. Goddard;
Alan D. Goddard
§Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
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Stuart J. Ferguson;
Stuart J. Ferguson
§Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, U.K.
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M. Dolores Roldán;
M. Dolores Roldán
‡Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, Edificio Severo Ochoa, 1 planta, Campus de Rabanales, Córdoba 14071, Spain
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David J. Richardson
David J. Richardson
2
*Centre for Molecular and Structural Biochemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, U.K.
†School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, U.K.
2To whom correspondence should be addressed (email d.richardson@uea.ac.uk).
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Biochem J (2011) 435 (3): 743–753.
Article history
Received:
November 30 2010
Revision Received:
February 11 2011
Accepted:
February 24 2011
Accepted Manuscript online:
February 24 2011
Citation
Andrew J. Gates, Victor M. Luque-Almagro, Alan D. Goddard, Stuart J. Ferguson, M. Dolores Roldán, David J. Richardson; A composite biochemical system for bacterial nitrate and nitrite assimilation as exemplified by Paracoccus denitrificans. Biochem J 1 May 2011; 435 (3): 743–753. doi: https://doi.org/10.1042/BJ20101920
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