Over-production and Characterization of the nifA Gene Product of Klebsiella pneumoniae -- the Transcriptional Activator of nif Gene Expression

The nifA gene of Klebsiella pneumoniae, which encodes the transcriptional activator of nif gene expression, was cloned into a number of plasmid vectors to obtain high-level synthesis of nifA product (NifA). When over-produced, NifA was very insoluble and it precipitated with the cell debris after cell lysis. Localization of beta-galactosidase activity from a nifA-lacZ translational fusion confirmed the insoluble nature of NifA. Analysis of two translational fusions in which the last six C-terminal amino acids of NifA were deleted suggests that these residues are required for activity.