Author/Authors :
Pedrosa، نويسنده , , F.O. and Teixeira، نويسنده , , K.R.S. and Machado، نويسنده , , I.M.P. and Steffens، نويسنده , , M.B.R. and Klassen، نويسنده , , G. and Benelli، نويسنده , , E.M. and Machado Neto، نويسنده , , H.B. and Funayama، نويسنده , , S. and Rigo، نويسنده , , L.U. and Ishida، نويسنده , , M.L. and Yates، نويسنده , , Ieda M.G. and Souza، نويسنده , , E.M.، نويسنده ,
Abstract :
The promoter regions of nifA and nifH genes of Herbaspirillom seropedicae have been isolated and investigated, and the nifA promoter has been characterized in detail. Both regions contain a −24−12 type promoter and NifA-binding sites; the nifA promoter also has an NtrC-binding site. The nifA expression is activated by NtrC and repressed by ammonium ions but not by oxygen. When the NtrC-binding site was deleted nifA expression was NifA-dependent. The native NifA protein of H. seropedicae was unable to activate nifH expression in Escherichia coli whereas a truncated protein, lacking the N-terminal domain was able to activate nifH expression in the absence of oxygen and presence of iron, indicating that the N-terminal domain regulates NifA activity. The truncated protein also activates nifH in Azospirillum brasilense in the presence or absence of ammonium ions. This suggests that the N-terminal domain senses the nitrogen status of the cell.
