FIG. 1.

PPIase activities of SlyD variants. Upon addition of 1 μM wild-type (WT) SlyD or a SlyD mutant [SlyD(I42S) or SlyD(I42S F132Y)] to 71.3 μM substrate (succinyl-Ala-Phe-Pro-Phe-4-nitroanilide), the decrease in absorbance at 330 nm was monitored for 80 s in 35 mM HEPES, pH 7.6, at 10°C (13). Kinetic traces were fit to a single exponential decay equation, and the value observed in the absence of protein was subtracted, followed by normalization to the enzyme concentration. Data are averages of the values from at least three independent measurements that were normalized to the value for wild-type SlyD (3 × 10⁴ M⁻¹ s⁻¹). Error bars, ±1 standard deviation.