FIG. 7.

Model for the role of PucR in the regulation of purine degradation in B. subtilis under nitrogen-limiting conditions with purine degradation products (e.g., allantoin) available. TnrA induces transcription from pucR, and PucR induces transcription from the purine catabolic genes, as purine degradation products are available. PucR also inhibits its own transcription and transcription from the pucABCDE operon. The sizes of and distances between genes and operons are not drawn to scale. Short bent arrows indicate promoters; long arrows indicate induction; lines ending in a bar indicate repression; boxes denote genes or operons.