Figure 6.

(A) Proposed adducts between CBXs and oligopeptides (UP1, CGKGCGSGYGW; UP2, AGKGCGSGYGW), i.e., irreversible thiazoline with N-terminal Cys and reversible thioimidate with internal Cys. UP1 adducts with monolabeled internal residues were not detected. (B) UHPLC chromatograms at 280 nm for the Cys treatment experiment with compound 52. Oligopeptides were incubated with the compound for 30 min at 37 °C; then, Cys was added and incubated for another 30 min. Full chromatograms are provided in the Supporting Information, Figure S21 and Oligopeptide Labeling. (C) Correlation between k₂ with Cys (Figure 5) and conversion of UP2 oligopeptide without the N-terminal Cys.