Figure 1.

Kinase-catalyzed photo-cross-linking with peptide substrates. a) CK2 or b) Abl kinase was incubated with the rhodamine-labeled CK2 substrate peptide 14 (Rho-14) or the ROX-labeled Abl substrate peptide 13 (ROX-13), respectively, in the presence of ATP (1) or ATP-ArN₃ (3). The resulting mixtures were separated by SDS-PAGE and visualized by in-gel fluorescence scanning (a and b, top), Coomassie staining (a, bottom), or silver staining (b, bottom). Reaction mixtures were incubated either with or without exposure to UV light (365 nm). TFA was added to a final concentration of 50% after cross-linking (lane 7). The appearance of CK2 as a double band is probably due to limited proteolysis of the catalytic subunit.[18] The gels are representative of at least three independent experiments.