Fig. 1.

FP labeling of Arabidopsis leaf extracts. A, structures of the activity-based probes used in this study. All carry an FP reactive group, and some have a PEG (p) linker or hydrocarbon linker and either Bio or Rh reporter tags or both (TriFP). Complete structures are given in supplemental Fig. S1. B, comparison of labeling with FP with and without PEG linker. Arabidopsis leaf extracts were preincubated with or without 20 μm FPpBio or preheated (10 min at 90 °C) and labeled with 2 μm FPpRh or FP-Rh for 2 h. Proteins were separated on large protein gels, and fluorescent signals were detected by fluorescence scanning. C, FP labeling profile is pH-dependent. Arabidopsis leaf extracts were labeled with FP-Rh at various pH values and analyzed on protein gels by fluorescence scanning. Arrow, Rubisco.