Component of the phosphoenolpyruvate-dependent nitrogen-metabolic phosphotransferase system (nitrogen-metabolic PTS), that seems to be involved in regulating nitrogen metabolism. Enzyme I-Ntr transfers the phosphoryl group from phosphoenolpyruvate (PEP) to the phosphoryl carrier protein (NPr). Could function in the transcriptional regulation of sigma-54 dependent operons in conjunction with the NPr (PtsO) and EIIA-Ntr (PtsN) proteins. Enzyme I-Ntr is specific for NPr. L-histidyl-[protein] + phosphoenolpyruvate = N(pros)-phospho-L-histidyl-[protein] + pyruvate The EI N-terminal domain contains the HPr binding site, the central domain the pyrophosphate/phosphate carrier histidine, and the C-terminal domain the pyruvate binding site. The GAF domain is an important site of signal perception in prokaryotes and eukaryotes. The reaction takes place in three steps, mediated by a phosphocarrier histidine residue located on the surface of the central domain. The two first partial reactions are catalyzed at an active site located on the N-terminal domain, and the third partial reaction is catalyzed at an active site located on the C-terminal domain. For catalytic turnover, the central domain swivels from the concave surface of the N-terminal domain to that of the C-terminal domain. Belongs to the PEP-utilizing enzyme family.