Involved in the regulation of glucose metabolism. Represses its own expression as well as that of the gluconate permease GntP (PubMed:28752954). It employs an effector mediated de-repression mechanism: in the absence of ligand, GntR binds to the gntR and gntP promoters and represses their expression. The release of promoter bound GntR is induced by gluconate and 6-phosphogluconate that bind with similar apparent affinities to the GntR/DNA complex. The release of GntR leads to transcription of the genes (PubMed:28752954). Free GntR fails to recognize gluconate and 6-phosphogluconate, whereas the GntR/DNA complexes recognize both ligands. It is therefore likely that GntR DNA binding induces structural changes that permit GntR to recognize effectors. Negatively autoregulated.