Redox and spectroscopic properties of the Escherichia coli nitric oxide-detoxifying system involving flavorubredoxin and its NADH-oxidizing redox partner |
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Authors: | Vicente João B Teixeira Miguel |
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Institution: | Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, Apt. 127, 2781-901 Oeiras, Portugal. |
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Abstract: | Under anaerobic conditions, the flavodiiron NO-reductase from Escherichia coli (flavorubredoxin, FlRd) constitutes one of the major protective enzymes against nitric oxide. The redox and spectroscopic properties of the rubredoxin (Rd), non-heme diiron, and FMN sites of flavorubredoxin were determined, which was complemented by the study of truncated versions of FlRd: one consisting only of its rubredoxin module, and another consisting of its flavodiiron structural core (lacking the Rd domain). The studies here reported were performed by a combination of potentiometry with visible and EPR spectroscopies. Moreover, we present the first direct EPR evidence for the presence of the non-heme diiron site in the flavodiiron proteins family. Also, the redox properties of the FlRd physiological partner, the NADH:flavorubredoxin oxidoreductase (FlRd-Red), were determined. It is further shown that the redox properties of this complex electron transfer system are fine-tuned upon interaction of the two enzymes. |
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