Figure 3.

Evidence that skpo-1 is a potential peroxidase. (A) Peroxidase domain sequences were aligned against the putative peroxidase domain of SKPO-1. SKPO-1 possesses the distal histidine (H²²²), catalytic arginine (R³³²), and proximal histidine (H⁴²⁸), which are necessary for peroxidase activity. However, SKPO-1 lacks covalent heme-binding residues (S²²¹ and L³³⁵) that are characteristic of mammalian peroxidases (Ortiz de Montellano 2008). (B) eri-1 mutant worms were grown on VC RNAi or skpo-1 RNAi prior to exposure with either E. coli or E. faecalis for 12 hr at 25°. (C) Wild-type and skpo-1 mutant worms were grown on cdc-25.1 RNAi prior to exposure with either E. coli or E. faecalis for 12 hr at 25°. (B and C) Following exposure to E. coli or E. faecalis, the amount of H₂O₂ produced per minute was determined using the Amplex Red assay. Error bars represent the SEM and the asterisks indicate significant differences between eri-1 worms exposed to VC RNAi or skpo-1 RNAi that were infected with E. faecalis as well as between wild-type and skpo-1 mutant worms exposed to cdc-25.1 RNAi prior to infection with E. faecalis [P = 0.0091 (B) and P < 0.0001 (C)]. Additionally, wild-type and skpo-1 mutant worms were exposed to 80 μM diphenyleneiodinium chloride (DPI) and H₂O₂ levels were calculated for both E. coli- and E. faecalis-exposed animals (EC, P = 0.0752; EF, P = 0.4161, respectively) P-values were calculated via Student’s paired t-test. Data in B and C are representative of at least two independent replicates.