Chemical Modification of Fusion Protein Based on the Thermus thermophilus GroEL Chaperon with AEBSF Protease Inhibitor

Protease inhibitors are routinely used to prepare functional, full-size proteins. Here, we describe modifications of the chimeric protein based on the GroEL chaperon from Thermus thermophilus . Modifications of this chimeric protein resulted from its interaction during sample preparation with an irreversible inhibitor of serine proteases, 4-(2-Aminoethyl)benzenesulfonyl fluoride hydrochloride (AEBSF), which belongs to the sulfonyl-fluoride class of compounds. Protein samples were then identified via MALDI-TOF/TOF after in-gel preparation with trypsin. Modifications of tyrosine and lysine amino acid residues were shown to be present. Also, the availability of the tyrosine residue was found to be a prerequisite for its modification.