1. Mechanism of PRPP-mediated regulation of transcription by PyrR and PurR.
Mechanism of PRPP-mediated regulation of transcription by PyrR and PurR. PyrR and PurR are shown as orange spheres. (A) Model of PyrR regulation based on the combined data from B. subtilis and B. caldolyticus. RNA (green hairpin) binds to dimeric PyrR, which is stabilized by UMP, UTP, or PRPP. The tetrameric conformation is stabilized by GMP and does not bind RNA. See the text for details. (B) Model of PurRBs repression. DNA (blue line) containing one strong (solid green line) and one weak (green punctuated line) PurBox binds to two PurRBs dimers (forming a weak tetramer) in the absence of PRPP. In the presence of PRPP, the DNA binding is prevented and the tetramerization is lost. (C) Model of PurRLl activation. PurRLl binds to PurBox sequences, irrespective of PRPP binding, presumably as a dimer. Binding of PRPP is hypothesized to expose a binding site for RNA polymerase. RNA polymerase is positioned correctly relative to the −10 region of the promoter.
Bjarne Hove-Jensen et al. Microbiol. Mol. Biol. Rev. 2017; doi: /MMBR