Peroxynitrite-mediated post-translational modification of human glutamine synthetase

The aim of the project was to understand the mechanisms that underlie the oxidative inactivation of human glutamine synthetase (HsGS). For that purpose, we expressed and purified recombinant HsGS, exposed it in phosphate buffer to peroxynitrite (ONOO-) and assessed the functional and structural consequences. To characterize the oxidative post-translational modifications induced by ONOO-, several approaches were carried out (e.g. SDS-PAGE, western-blot, amino acid quantification by LC, etc). The most detailed characterization was performed through LC-MS/MS analysis after trypsin digestion of the ONOO--treated protein, which allowed us to identify the amino acid residues that are modified and to estimate the extent of such modifications.