title: Regulation of nitrogen fixation in Azospirillum brasilense.
abstract: The regulation of nitrogen fixation in Azospirillum brasilense is very complicated, and it responds to exogenous fixed nitrogen or a change of oxygen concentration. This regulation occurs at both transcriptional and posttranslational levels. Unlike regulation seen in Klebsiella pneumoniae, transcription of nifA does not require NTRB/NTRC in A. brasilense and the expression of nifHDK is controlled by posttranslational regulation of NIFA activity. Addition of NH4+ or a shift from microaerobic to anaerobic conditions also causes a rapid loss of nitrogenase activity in A. brasilense. This posttranslational regulation of nitrogenase activity involves the DRAT/DRAG regulatory system, which is similar to that of Rhodospirillum rubrum. Both DRAT and DRAG activities are regulated in vivo, but the mechanisms for their regulation are unknown.
authors.affiliation: Department of Biochemistry, University of Wisconsin-Madison 53706, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: R H
authors.initials: RH
authors.lastname: Burris
authors.forename: P W
authors.initials: PW
authors.lastname: Ludden
authors.forename: G P
authors.initials: GP
authors.lastname: Roberts
mesh_terms: D015806:Azospirillum brasilense / Q000502:physiology*; D001426:Bacterial Proteins / Q000378:metabolism; D017037:Dinitrogenase Reductase / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D009586:Nitrogen Fixation / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D017037:Dinitrogenase Reductase; C061338:NifA protein, Bacteria; D014157:Transcription Factors