The N-terminal domain of NifA determines the temperature sensitivity of NifA in Klebsiella pneumoniae and Enterobacter cloacae

The NifA protein is the central regulator of the nitrogen fixation genes. I t activates transcription of nif genes by an alternative holoenzyme form of RNA polymerase containing the delta(54) factor. The NifA protein from Kleb siella pneumoniae consists of the N-terminal domain of unknown function, th e central catalytic domain with ATPase activity and the C-terminal DNA-bind ing domain. The Kp NifA protein is sensitive to temperature, while the Ente robacter cloacae NifA protein is less sensitive to temperature than Kp NifA . Our results show that the N-terminal domain of NifA plays the decisive ro le in the temperature sensitivity of the protein.