PMID:17507380
| Citation |
Strube, K, de Vries, S and Cramm, R (2007) Formation of a dinitrosyl iron complex by NorA, a nitric oxide-binding di-iron protein from Ralstonia eutropha H16. J. Biol. Chem. 282:20292-300 |
|---|---|
| Abstract |
In Ralstonia eutropha H16, two genes, norA and norB, form a dicistronic operon that is controlled by the NO-responsive transcriptional regulator NorR. NorB has been identified as a membrane-bound NO reductase, but the physiological function of NorA is unknown. We found that, in a NorA deletion mutant, the promoter activity of the norAB operon was increased 3-fold, indicating that NorA attenuates activation of NorR. NorA shows limited sequence similarity to the oxygen carrier hemerythrin, which contains a di-iron center. Indeed, optical and EPR spectroscopy of purified NorA revealed the presence of a di-iron center, which binds oxygen in a similar way as hemerythrin. Diferrous NorA binds two molecules of NO maximally. Unexpectedly, binding of NO to the diferrous NorA required an external reductant. Two different NorA-NO species could be resolved. A minor species (up to 20%) showed an S = (1/2) EPR signal with g( perpendicular) = 2.041, and g( parallel) = 2.018, typical of a paramagnetic dinitrosyl iron complex. The major species was EPR-silent, showing characteristic signals at 420 nm and 750 nm in the optical spectrum. This species is proposed to represent a novel dinitrosyl iron complex of the form Fe(2+)-[NO](2)(2-), i.e. NO is bound as NO(-). The NO binding capacity of NorA in conjunction with its high cytoplasmic concentration (20 mum) suggests that NorA regulates transcription by lowering the free cytoplasmic concentration of NO. |
| Links |
PubMed Online version:10.1074/jbc.M702003200 |
| Keywords |
Bacterial Proteins/metabolism; Carrier Proteins/metabolism; Cupriavidus necator/physiology; Hemerythrin/metabolism; Iron/metabolism; Nitric Oxide/metabolism; Operon/physiology; Oxidoreductases/biosynthesis; Sequence Homology, Amino Acid; Transcription Factors/metabolism; Transcription, Genetic/physiology |
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