Fig. 5.
Structures of the glycine vinylmethyl ester (HAUbVME) and bromoethylamide [HAUbBr(2)]-derived probes used in this study to covalently modify USPs. Chemoselective alkylation by way of Michael addition to HAUbVME or by way of nucleophilic displacement of the bromine atom in HAUbBr(2) covalently modifies the catalytically active cysteine residue of USPs, in an activity-based manner. The formed covalent adducts can be used in immunoblotting or immunoprecipitation protocols, taking advantage of the hemagglutinin epitope present in the probe.