Is the main repressor of the genes involved in the de novo synthesis of purine nucleotides, regulating purB, purC, purEK, purF, purHD, purL, purMN and guaBA expression. PurR is allosterically activated to bind its cognate DNA by binding the purine corepressors, hypoxanthine or guanine, thereby effecting transcription repression. Purine metabolism; purine nucleotide biosynthesis [regulation]. Homodimer. Consists of two structural and functional domains: an N-terminal DNA-binding domain, approximately the first 60 residues, and a larger C-terminal domain, approximately 280 residues, which imparts the function of corepressor binding and oligomerization.