Transcription repressor that represses many genes including ureABC and tnrA, during nitrogen excess (PubMed:2573733, PubMed:1677938, PubMed:10231480, PubMed:18331450). On the contrary of the MerR members, which require longer DNA sites for high-affinity binding, GlnR requires a DNA sequence of 17 nucleotides as minimal binding site (PubMed:10231480, PubMed:25691471). Under conditions of nitrogen excess, the DNA binding activity of GlnR is activated by a transient interaction with feedback-inhibited GlnA (PubMed:18331450). Under conditions of nitrogen-limited, GlnR is autoinhibited by its C-terminal region (PubMed:25691471). Homodimer under conditions of nitrogen excess (PubMed:1677938, PubMed:18331450, PubMed:25691471). Monomer under conditions of nitrogen-limited (PubMed:25691471). Interacts with feedback-inhibited GlnA in order to stabilizes GlnR-DNA complex (PubMed:1677938, PubMed:18331450, PubMed:25691471). Under conditions of nitrogen-limited growth, repressed by TnrA. In vivo, this mutant constitutively represses glnR expression. In vitro, this mutant binds DNA more tightly than wild-type and this binding is not activated by feedback-inhibited GlnA. The amino acid sequences of the N-terminal DNA binding domains of TnrA and GlnR are highly similar, and both proteins bind to DNA sequences with a common consensus sequence. In contrast, the C-terminal signal transduction domains of TnrA and GlnR have no homology.