Involved in the regulation of 3-chlorocatechol degradation. Transcriptional regulator of tfdB expression. Acts as a repressor in the absence of its effector (either 2-cis-chlorodiene lactone or chloromaleylacetate) but acts as an activator when its effector is present. Belongs to the LysR transcriptional regulatory family. The products of the genes tfdR and tfdS were originally thought to be identical but in fact they differ by one residue (amino acid 264 which is Asp in tfdR and Ala in tfdS).