FRET assay with PI-2a peptides for substrate specificity analysis of SrtA_ΔN40.

<p>The reaction solutions contained 256 µM of fluorescent peptide, 3 µM of SrtA_ΔN40 and 75 mM of triglycine as peptidoglycan analogue. The reactions were performed at 37°C in the assay buffer containing 20 mM HEPES, pH 7.5. We monitored fluorescence emission every 5 minutes and we observed an increase in fluorescence intensity only in the presence of AP2-2a peptide (filled squares), as opposed to BP-2a peptide (open squares) and AP1-2a peptide (filled triangles). In the presence of an additional variation of AP2-2a motif (AP2-2a_mut, open circles) the reaction did not occur.