Fig. 9.

Proposed model for D. radiodurans survivorship in part due to activation of the PprI-mediated functional pathways in response to irradiation. Irradiation produces various cellular damage signals. PprI may directly sense those signals or be activated by other intermediate sensors. The activated PprI partly controls the stress response pathway and also switches on many defense pathways. The DNA repair system is one of the major pathways that is activated by PprI. It enhances the scavenging capacity for reactive oxygen species (19) by switching on catalase E. It up-regulates protein expression in several protein synthesis and recycling pathways. The activated transcription, translation, and post-translational systems subsequently work together to produce more defense proteins, proteases responsible for degrading damaged proteins, and proteins working in energy metabolism, all of which participate in cell survival from radiation damage directly or indirectly.