Main transcriptional repressor of genes involved in N-acetylglucosamine (GlcNAc) transport and utilization (PubMed:21602348, PubMed:20047956, PubMed:24673833). Represses the expression of the nagAB and nagP operons by binding directly within their upstream regions (PubMed:21602348, PubMed:24673833). Binds to the DNA consensus sequence 5'-ATTGGTATAGACAACT-3' (PubMed:21602348). Also acts as a weak repressor of mapB expression (PubMed:16207374). Binding to DNA is allosterically inhibited by an effector molecule (PubMed:20047956, PubMed:21602348, PubMed:24673833, PubMed:25564531). Binding of the effector to the C-terminal domain leads to a conformational change that modulates binding to DNA and thereby regulates transcription of the target genes (PubMed:20047956, PubMed:25564531). Glucosamine-6-phosphate (GlcN6P) and/or N-acetylglucosamine-6-phosphate (GlcNAc6P) are putative effectors of NagR (PubMed:20047956, PubMed:21602348, PubMed:24673833, PubMed:25564531). Binding of GlcNAc6P may prevent the protein-protein interactions responsible for polymerization along the DNA, but not the specific DNA binding (PubMed:24673833). Homodimer (PubMed:19342794, PubMed:20047956, PubMed:25564531). Forms dimers via the C-terminal effector-binding domain (PubMed:20047956). At high concentrations, probably forms polymers along the DNA (PubMed:24673833). The N-terminal region contains a canonical wHTH DNA-binding domain. It is linked via a 21 residue-long linker to the C-terminal domain, which binds the effector molecule. Deletion of the gene results in the modulation of the expression of many important genes, probably indirectly due to an excess of the crucial molecules acetate, ammonia, and fructose-6-phosphate, resulting from complete hydrolysis of GlcNAc (PubMed:21602348). Disruption of the gene induces a slight but consistent increase in MapB activity (PubMed:16207374).