In vitro transcription of the nitrogen fixation regulatory operon nifLA of Klebsiella pneumoniae.

In vitro transcription from the promoter for the nitrogen fixation regulatory operon nifLA of K. pneumoniae requires four protein fractions: the core form of RNA polymerase; NTRA, an alternate sigma factor; NTRC, an auxiliary DNA-binding protein; and NTRB, a bifunctional enzyme that controls the activity of NTRC by covalent modification (A.J. Ninfa and B. Magasanik, Proc. Natl. Acad. Sci. USA 83:5909, 1986). Two DNA-binding sites for NTRC lie approximately 150 base pairs upstream of the nifLA promoter.