Identification of S-glutathionylated cellular proteins during oxidative stress and constitutive metabolism by affinity purification and proteomic analysis

Redox modification of proteins is proposed to play a central role in regulating cellular function. However, high-throughput techniques for the analysis of the redox status of individual proteins in complex mixtures are lacking. The aim was thus to develop a suitable technique to rapidly identify proteins undergoing oxidation of critical thiols by S-glutathionylation. The method is based on the specific reduction of mixed disulfides by glutaredoxin, their reaction with N-ethylmaleimide–biotin, affinity purification of tagged proteins, and identification by proteomic analysis. The method unequivocally identified 43 mostly novel cellular protein substrates for S-glutathionylation. These include protein chaperones, cytoskeletal proteins, cell cycle regulators, and enzymes of intermediate metabolism. Comparisons of the patterns of S-glutathionylated proteins extracted from cells undergoing diamide-induced oxidative stress and during constitutive metabolism reveal both common protein substrates and substrates failing to undergo enhanced S-glutathionylation during oxidative stress. The ability to chemically tag, select, and identify S-glutathionylated proteins, particularly during constitutive metabolism, will greatly enhance efforts to establish posttranslational redox modification of cellular proteins as an important biochemical control mechanism in coordinating cellular function.