8 - Study towards 3-Aminotyrosine Containing Protein Labeling

Abstract

Protein tyrosine nitration, which involves the installation of a nitro group to the phenolic OH group of tyrosine at the ortho position, is an important post-translational modification (PTM) in biology. Although protein tyrosine nitration has been currently defined as a stable PTM, there is increasing evidence indicating that some of the tyrosine nitration processes are reversible in vivo, probably through formation of 3-aminotyrosine (3AT) residue in a reductant-dependent pathway. In addition, derivatization of 3AT-containing proteins, which are obtained from reduction of nitrated proteins in vitro, is an important step in proteomic study of protein nitration. Therefore, chemical labeling and enrichment of 3AT-containing proteins under physiological conditions are critical for investigations on protein tyrosine nitration and denitration. However, selective labeling of 3AT-containing proteins in aqueous medium under mild conditions has been particularly challenging due to potential interference from cysteine and other amino acids. Here we report novel chemical probes for labeling 3AT-containing proteins with fluorophore or biotin in aqueous medium under physiological conditions. It is expected that such probes will be applicable to further investigation on protein denitration processes in biological system.