Fnr Is required for NifL-dependent oxygen control of nif gene expression in Klebsiella pneumoniae.

ABSTRACT: In Klebsiella pneumoniae, NifA-dependent transcription of nitrogen fixation (nif) genes is inhibited by NifL in response to molecular oxygen and combined nitrogen. We recently showed that K. pneumoniae NifL is a flavoprotein, which apparently senses oxygen through a redox-sensitive, conformational change. We have now studied the oxygen regulation of NifL activity in Escherichia coli and K. pneumoniae strains by monitoring its inhibition of NifA-mediated expression of K. pneumoniae phi (nifH'-'lacZ) fusions in different genetic backgrounds. Strains of both organisms carrying fnr null mutations failed to release NifL inhibition of NifA transcriptional activity under oxygen limitation: nif induction was similar to the induction under aerobic conditions. When the transcriptional regulator Fnr

SUBMITTER: Grabbe R 

PROVIDER: S-EPMC95013 | biostudies-literature | 2001 Feb

REPOSITORIES: biostudies-literature