Mimicking phosphorylation of threonine 147 in vivo restores NADPH oxidase activity. CHO 91/47/67 expressing no p22phox (Mock), wild type (wtp22), T147A, or T147D p22phox were resuspended at 2 × 106 cells/ml and stimulated for 2 h with 100 nm PMA in the presence of 100 μl of Diogenes. Activity was measured according “Experimental Procedures.” Data represent three separate transfections and are shown as the mean ± S.E. (error bars) of the RLU/min. *, p < 0.05. NS, not significant. Western blot analysis probing for total p22phox expression is shown below the bars for one of the three experiments.