EPR and redox properties of periplasmic nitrate reductase from Desulfovibrio desulfuricans ATCC 27774.
Nitrate reductases are enzymes that catalyze the conversion of nitrate to nitrite. We report here electron paramagnetic resonance (EPR) studies in the periplasmic nitrate reductase isolated from the sulfate-reducing bacteria Desulfovibrio desulfuricans ATCC 27774. This protein, belonging to the dimethyl sulfoxide reductase family of mononuclear Mo-containing enzymes, comprises a single 80-kDa subunit and contains a Mo bis(molybdopterin guanosine dinucleotide) cofactor and a [4Fe-4S] cluster. EPR-monitored redox titrations, carried out with and without nitrate in the potential range from 200 to -500 mV, and EPR studies of the enzyme, in both catalytic and inhibited conditions, reveal distinct types of Mo(V) EPR-active species, which indicates that the Mo site presents high coordination flexibility. These studies show that nitrate modulates the redox properties of the Mo active site, but not those of the [4Fe-4S] center. The possible structures and the role in catalysis of the distinct Mo(V) species detected by EPR are discussed.
González
Pablo J
PJ
REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal.
Rivas
María G
MG
Brondino
Carlos D
CD
Bursakov
Sergey A
SA
Moura
Isabel
I
Moura
José J G
JJ
D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry*; D001665:Binding Sites; D002384:Catalysis; D045285:Desulfovibrio desulfuricans / Q000201:enzymology*; D004578:Electron Spin Resonance Spectroscopy; D006150:Guanine Nucleotides / Q000737:chemistry; D008982:Molybdenum / Q000737:chemistry; D050901:Nitrate Reductase / Q000037:antagonists & inhibitors / Q000737:chemistry*; D009566:Nitrates / Q000737:chemistry; D010084:Oxidation-Reduction; D019897:Periplasm / Q000201:enzymology; D011622:Pterins / Q000737:chemistry
D001426:Bacterial Proteins; D006150:Guanine Nucleotides; D009566:Nitrates; D011622:Pterins; C063761:molybdopterin guanine dinucleotide; D008982:Molybdenum; D050901:Nitrate Reductase