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Expression and characterization of the assimilatory NADH-nitrite reductase from the phototrophic bacterium Rhodobacter capsulatus E1F1 |
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| Authors: | M Francisca Olmo-Mira Purificación Cabello Carmen Pino Manuel Martínez-Luque David J Richardson Francisco Castillo M Dolores Roldán Conrado Moreno-Vivián |
| Institution: | (1) Departamento de Bioquímica y Biología Molecular, Universidad de Córdoba, Edificio Severo Ochoa, 1a planta, Campus de Rabanales, Córdoba, 14071, Spain;(2) Departamento de Botánica, Ecología y Fisiología Vegetal, área de Fisiología Vegetal, Universidad de Córdoba, Edificio Celestino Mutis, 3a planta, Campus de Rabanales, Córdoba, 14071, Spain;(3) School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, UK |
| Abstract: | A nas gene region from Rhodobacter capsulatus E1F1 containing the putative nasB gene for nitrite reductase was previously cloned. The recombinant His6-NasB protein overproduced in E. coli showed nitrite reductase activity in vitro with both reduced methyl viologen and NADH as electron donors. The apparent K m values for nitrite and NADH were 0.5 mM and 20 μM, respectively, at the pH and temperature optima (pH 9 and 30°C). The optical spectrum showed features that indicate the presence of FAD, iron-sulfur cluster and siroheme as prosthetic groups, and nitrite reductase activity was inhibited by sulfide and iron reagents. These results indicate that the phototrophic bacterium R. capsulatus E1F1 possesses an assimilatory NADH-nitrite reductase similar to that described in non-phototrophic organisms. |
| Keywords: | NADH-nitrite reductase Nitrate assimilation Phototrophic bacteria Siroheme |
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