Member of the two-component regulatory system NtrB/NtrC, which controls expression of the nitrogen-regulated (ntr) genes in response to nitrogen limitation. Phosphorylated NtrC binds directly to DNA and stimulates the formation of open promoter-sigma54-RNA polymerase complexes (PubMed:2874557, PubMed:3304660, PubMed:2574599, PubMed:1350679). Activates transcription of many genes and operons whose products minimize the slowing of growth under nitrogen-limiting conditions, including genes coding for glutamine synthetase (glnA), transporters, amino acid permeases and catabolic enzymes (PubMed:11121068). Homodimer. Phosphorylation of the N-terminal receiver domain leads to the formation of oligomers (PubMed:1350679). Can also form phosphorylation-independent oligomers (PubMed:15208307). Contains an N-terminal receiver domain, a central output domain, which hydrolyzes ATP, interacts with RNA polymerase and is required for phosphorylation-dependent oligomerization, and a C-terminal domain, which is involved in DNA binding, dimerization and phosphorylation-independent oligomerization. Phosphorylated and dephosphorylated by NtrB (PubMed:2874557, PubMed:2574599). Phosphorylation induces strong cooperative binding to DNA (PubMed:1350679).