Efficient approach for profiling photoaffinity labeled peptides with a cleavable biotinyl photoprobe

Based on the application of our recent biotinyl photoprobe with a cleavable N-acylsulfonamide, an efficient process has been developed for profiling photoaffinity labeled peptides among a large excess of unlabeled concomitants. N-acylsulfonamide group was found to be stable under the usual S-pyridylethylation condition of cysteine residues whereas the group was easily cleaved by N-alkylation with iodoacetic acid in acidic condition. The selective nature between two common protein alkylation reactions was evaluated with l-glutamate dehydrogenase (GDH) using an acidic amino acid photoprobe with biotinylated acylsulfonamide function. The labeled GDH was successfully subjected to S-pyridylethylation keeping the biotin tag intact, and then was easily released from streptavidin matrix with high purity via iodoacetic acid-mediated alkylation under mild condition at pH 5.0.