Formation of a dinitrosyl iron complex by NorA, a nitric oxide-binding di-iron protein from Ralstonia eutropha H16.
J Biol Chem
; 282(28): 20292-300, 2007 Jul 13.
Article
em En
| MEDLINE
| ID: mdl-17507380
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.
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Coleções:
01-internacional
Temas:
Agentes_cancerigenos
Base de dados:
MEDLINE
Assunto principal:
Proteínas de Bactérias
/
Fatores de Transcrição
/
Proteínas de Transporte
/
Cupriavidus necator
/
Ferro
/
Óxido Nítrico
Tipo de estudo:
Prognostic_studies
Idioma:
En
Revista:
J Biol Chem
Ano de publicação:
2007
Tipo de documento:
Article
País de afiliação:
Alemanha