Function
Purine repressor (PurR) is a member of the lac repressor family. PurP binds DNA via a highly conserved helix-turn-helix at the N terminal (DBD). PurP contains a nucleotide co-repressor binding domain as well (CBD). PurP binds to a 16-bp operator sequence and co-regulates genes which are involved in the biosynthesis of purine and pyrimidine nucleotides[1].
Structural highlights
The PurP guanine co-repressor binding site includes stacking interactions as well as hydrogen bonded ones. The DNA binding domain contains a helix-turn-helix-loop-helix motif which interacts with the DNA major groove and a hinge helix binding to to the DNA minor groove. Residue L53 interdigitates with the DNA central base pair[2].
