Detection of S-glutathionylated proteins by glutathione S-transferase overlay.

Oxidative and nitrosative stress lead to the S-glutathionylation of proteins and subsequent functional impairment. Glutathione S-transferase (GST) from Schistosoma japonicum was found to bind to the glutathione moiety of S-glutathionylated proteins, thus establishing a convenient method for detecting S-glutathionylated proteins by biotinylated GST. Applications of this method to proteins that were prepared from cultured cells and blotted onto a membrane exhibited numerous positive bands, which were abolished by treatment with dithiothreitol. Treatment of a cellular extract with nitrosoglutathione led to enhanced staining of the bands in a dose-dependent manner. The method was also applicable for the histochemical detection of S-glutathionylated proteins in situ. The positive staining by biotin-GST became faint in the presence of S-glutathionylated ovalbumin, suggesting that the reaction is specific to S-glutathionylated proteins. Collectively, these data indicate that the method established here is simple and useful for detecting S-glutathionylated proteins on blotted membrane and in situ.