FIG 2 .

The noncanonical GTC sigR start codon is critical for correct and proper functioning of the oxidative stress regulatory system. (A) Automated Wes Western blot showing SigR levels in Δ(sigR-rsrA) null strain J2146 carrying the empty pRT801 integrative vector or parallel pRT801 constructs carrying the p1-sigR-rsrA operon with a GTC (wild type), ATG, GTG, or TTG start codon. The same amount (2.5 µg) of total protein of each sample was loaded, and SigR was detected with an anti-SigR polyclonal antibody. A single replicate of each strain is shown. (B) Quantitation of SigR levels (area under each peak; arbitrary units [A.U.]). All samples were analyzed in triplicate, and the mean value and standard error of each sample are shown. (C) Changing the natural sigR GTC start codon to any of the canonical start codons (ATG, GTG, or TTG) blocks sporulation, resulting in white colonies because of the absence of the gray spore pigment. Shown are colonies of Δ(sigR-rsrA) null strain J2146 carrying the empty pRT801 integrative vector or parallel pRT801 constructs carrying the p1-sigR-rsrA operon with a GTC (wild type), ATG, GTG, or TTG start codon grown on SFM and photographed after 4 days. wt, wild type.