Transcription repressor during nitrogen excess. 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. Under conditions of nitrogen excess, the DNA binding activity of GlnR is activated by a transient interaction with feedback-inhibited GlnA. Under conditions of nitrogen-limited, GlnR is autoinhibited by its C-terminal region. Homodimer under conditions of nitrogen excess. Monomer under conditions of nitrogen-limited. Interacts with feedback-inhibited GlnA in order to stabilizes GlnR-DNA complex. Under conditions of nitrogen-limited growth, repressed by TnrA. 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.