Zinc-responsive regulator that acts both as a repressor and as an activator by regulating directly the promoters of its target genes. In the presence of zinc, directly represses the expression of the adcRCBA operon, of genes coding for a group of surface antigen zinc-binding pneumococcal histidine triad proteins (PhtA, PhtB, PhtD and PhtE), and of adcAII. Can also activate expression of adh. Zinc acts as a coregulator and is required for DNA-binding activity (PubMed:20804771 and PubMed:21603707). Homodimer. The second zinc-binding site seems to play no significant role in the regulatory process. Its function is unknown (PubMed:22085181).