Fig. 3.

(A) Specificity profiling of chlamydial protease-like activity factor. The protease:library ratio was 1:500 (wt/wt). Incubation at pH 7.5 occurred for either 1 h or 16 h at 37 °C. P1 constitutes the major specificity determinant with a mixed preference for either small (alanine, glycine) or aliphatic (methionine) residues. (B and C) Negative correlation between P1 methionine and P2′ isoleucine. (D) Structural modeling of the peptide sequences VM↓VA or VM↓VI (“↓” indicates the cleavage site) in the active site of CPAF (“Ser” denotes active site serine 499).