Oligopeptide Inhibition of SrtA Mutants

The inhibitory effect of the oligopeptide against SrtA and its mutants activity was determined as previously described in 96-well black plates (PerkinElmer, Boston, MA, United States) (Wang et al., 2015c (link)). Briefly, 100 μL of purified SrtA (4 mM) was preincubated with 100 μL of increasing concentrations of the oligopeptide (3.125–25 μM) in reaction buffer at 37°C for 20 min. The model fluorescent peptide substrate Dabcyl-QALPTTGEE-Edans (GL Biochem, Shanghai, China) (final concentration of 10 μM) was added to the reaction system, followed by incubation at 37°C for 1 h. Fluorescence intensity was measured at emission and excitation wavelengths of 350 and 520 nm, respectively. The experiments were repeated three times independently for each sample.