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Braz. j. med. biol. res ; 45(12): 1135-1140, Dec. 2012. ilus, tab
Article Dans Anglais | LILACS | ID: lil-659653

Résumé

Azospirillum brasilense is a diazotroph that associates with important agricultural crops and thus has potential to be a nitrogen biofertilizer. The A. brasilense transcription regulator NifA, which seems to be constitutively expressed, activates the transcription of nitrogen fixation genes. It has been suggested that the nitrogen status-signaling protein GlnB regulates NifA activity by direct interaction with the NifA N-terminal GAF domain, preventing the inhibitory effect of this domain under conditions of nitrogen fixation. In the present study, we show that an N-terminal truncated form of NifA no longer required GlnB for activity and lost regulation by ammonium. On the other hand, in trans co-expression of the N-terminal GAF domain inhibited the N-truncated protein in response to fixed nitrogen levels. We also used pull-down assays to show in vitro interaction between the purified N-terminal GAF domain of NifA and the GlnB protein. The results showed that A. brasilense GlnB interacts directly with the NifA N-terminal domain and this interaction is dependent on the presence of ATP and 2-oxoglutarate.


Sujets)
Adénosine triphosphate/métabolisme , Azospirillum brasilense/enzymologie , Protéines bactériennes/métabolisme , Acides cétoglutariques/métabolisme , Facteurs de transcription/métabolisme , beta-Galactosidase/métabolisme , Azospirillum brasilense/métabolisme , Vecteurs génétiques , Plasmides
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