EP24.15 fragments containing S-glutathiolated Cys residues generated by trypsin hydrolysis and followed by Q-ToF analysis.

The wild type protein was treated with TCEP followed by 1 mM GSSG, as described in the Materials and Methods. Next, samples were digested with trypsin for Q-TOF analysis. Sequence coverage was 63%. Underlined and italic Cys notations were S-glutathiolated and reduced, respectively. Fragments containing the other eight EP24.15 Cys residues were not detected in this condition; those containing oxidized Cys residues to –SOH, SO2H or –SO3H were also investigated and not detected. Representative Q-ToF spectra detecting 305.1 mass additions are shown in Figure 1. 1The same residues were also S-glutathiolated after incubation with 50 µM GSSG.