Dual transcriptional regulator of the TyrR regulon, which includes a number of genes coding for proteins involved in the biosynthesis or transport of the three aromatic amino acids, phenylalanine, tyrosine and tryptophan (PubMed:4887504, PubMed:4399341, PubMed:334742, PubMed:1860819, PubMed:8449883, PubMed:7961453, PubMed:7798138, PubMed:14614536, PubMed:15049824). These three aromatic amino acids act as effectors which bind to the TyrR protein to form an active regulatory protein (PubMed:4399341, PubMed:334742, PubMed:1860819, PubMed:8106498, PubMed:7961453). Modulates the expression of at least eight unlinked transcription units, including aroF, aroG, aroLM, aroP, mtr, tyrA, tyrB and tyrP (PubMed:4887504, PubMed:4399341, PubMed:334742, PubMed:1860819, PubMed:8449883, PubMed:7961453, PubMed:7798138, PubMed:14614536, PubMed:15049824). In most cases TyrR acts as a repressor, but positive effects have been observed on the tyrP gene, which is repressed in the presence of tyrosine and activated at high phenylalanine concentrations (PubMed:334742, PubMed:1860819, PubMed:8449883, PubMed:7798138, PubMed:15049824, PubMed:8407813). Is also involved in activation, but not repression, of mtr expression in association with phenylalanine or tyrosine (PubMed:2061290, PubMed:8449883, PubMed:8407813). Acts by binding specifically to TyrR boxes in the promoter region of the target genes (PubMed:1860819, PubMed:8449883, PubMed:7961453, PubMed:8947567, PubMed:10197993). Binding of ATP strongly enhances the affinity of TyrR for tyrosine. Homodimer (PubMed:8106498, PubMed:8176727, PubMed:8947567, PubMed:11923293). In presence of tyrosine (or high concentrations of phenylalanine or tryptophan) and ATP, it self-associates to form an hexamer (PubMed:8176727, PubMed:8947567, PubMed:11923293). At low tyrosine concentrations, homodimers can bind to certain recognition sequences referred to as 'strong TyrR boxes' (PubMed:8176727). Homohexamers are the active repressing species, interacting with two or three tyrR boxes in the targeted regulatory DNA, including 'strong TyrR boxes' and lower-affinity sites called 'weak TyrR boxes' (PubMed:8176727). Interacts with its own promoter-operator region. Autogenously regulated by a mechanism that gives similar rates of expression of tyrR irrespective of concentration of the aromatic amino acids. Contains an N-terminal domain (1-190), a central domain (206-433) and a C-terminal region (444-513) (PubMed:8449883, PubMed:8444880, PubMed:17222426). The N-terminal domain is required for transcription activation functions, dimerization and ATP-independent aromatic amino acid binding (PubMed:8449883, PubMed:8407813, PubMed:8444880, PubMed:17222426, PubMed:30680497). The central domain is involved in ATP binding and hydrolysis, and is responsible for ATP-dependent tyrosine binding and hexamerization associated with tyrosine-mediated repression functions (PubMed:8449883, PubMed:8444880, PubMed:11923293). The C-terminal region contains a classical helix-turn-helix motif responsible for binding to DNA targets known as TyrR boxes (PubMed:8449883, PubMed:10197993). Regulation of individual transcription units within the regulon reflects their physiological function and is determined by the position and nature of the recognition sites (TyrR boxes) associated with each of the promoters.