Deletion analysis of the nitrogen fixation regulatory gene,nifL of Klebsiella pneumoniae

A number of in-frame deletions have been constructed in the Klebsiella pneumoniae regulatory gene nifL. The effects of each nifL mutation on NifA-mediated expression from the nifH promoter of K. pneumoniae have then been assessed with respect to both nitrogen and oxygen control. These experiments indicate that, in contrast to the situation with the homologous regulatory proteins NtrB and NtrC, NifA activity is not impaired in the absence of NifL. We conclude that the only function of NifL is to inactivate NifA in response to an increase in the nitrogen or oxygen status of the cell.