Positively regulates the expression of the exporter LysE and represses its own expression. Activity requires the presence of a coinducer, lysine or histidine. Acts by binding to lysG-lysE promoter region. Also up-regulates the expression of ppsB, ppsC and ppsD, by binding to the upstream region of ppsB. Homodimer (PubMed:20036253). Two types of dimers are identified from the crystal packing: a DBD-type dimer, where the dimer is mainly stabilized by the coiled-coil linker helices, and a RD-type dimer, where RDs contact each other in an antiparallel, side-by-side alignment (PubMed:20036253). Negatively autoregulated. Contains an N-terminal DNA binding domain (DBD) and a C-terminal regulatory domain (RD). A wide array of epitopes was recognized on Rv1985c in TB patients. Those epitopes could specifically discriminate TB infection from BCG vaccination. These results indicate that the peptide pools selected from Rv1985c have the potential to diagnose TB infection by a method that may be routinely used in clinical laboratories. Belongs to the LysR transcriptional regulatory family.