Figure 2. Transcriptional activity of NifA variant proteins in Escherichia coli JM109 (DE3) carrying pRT22 (nifH::lacZ). (-) indicates cells carrying pET-29a. Full-length NifA was expressed from pRAM1. ΔN-NifA indicates an N-truncated form of NifA expressed from pRAM2. Full-length NifA mutants, as indicated, were expressed from pET-29a-based plasmids. β-galactosidase expression experiments were performed in NFDM medium (31) with 20 mM of ammonium chloride (+N) or 0.2% casamino acids (-N), in the absence of O2. Data are reported as the mean±SD of 3 independent assays. β-galactosidase activity is reported as Miller units.
