Figure 5

Schematic representation of oxidative stress metabolism and regulatory network in C. jejuni. The oxidants are highlighted in red; the anti-oxidant proteins are boxed in blue; and the transcriptional regulators, Fur and PerR, are boxed in green and gray, respectively. SodB catalyzes the dismutation of superoxide anion (^.O₂) to hydrogen peroxide (H₂O₂). KatA reduces H₂O₂ to water and oxygen. AhpC catalyzes the reduction of organic hydroperoxide (ROOH) and H₂O₂ to their corresponding alcohols. Note that H₂O₂ reduction is primarily catalyzed by KatA (blue arrow) and secondarily by AhpC (dashed blue arrow). Intracellular iron reacts with H₂O₂ and ROOH to produce hydroxyl radicals (^.OH) and alkoxyl radicals (RO^.), the two most toxic ROS. Fe²⁺-Fur is the primary repressor of iron-acquisition pathways (green lines), including ChuABCD, and is the secondary repressor of KatA (dashed green line). Fe²⁺-PerR is the primary repressor of KatA and AhpC (gray lines), and the secondary repressor of ChuABCD (dashed gray line). H₂O₂ disrupts the ability of PerR to act as a repressor. Iron represses PerR through an unidentified pathway. Heme is transported by ChuABCD and is required for KatA activity.