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. 2016 May 9;291(26):13699–13714. doi: 10.1074/jbc.M115.694422

FIGURE 2.

FIGURE 2.

6-TGNP, derived from 6-TG, targets Rac1 to produce 6-TGNP-Rac1 disulfide adduct in CD4+ cells. A, ESI-MS analyses of CD4+ cells for the detection of the 6-TGNP-Rac1 disulfide adduct were performed as described under “Experimental Procedures.” The MS peak at 1481.6 Da was only shown when CD4+ cells were treated with 6-TG (panel b) and not shown when CD4+ cells were not treated with 6-TG (panel a). B, MS/MS analysis was performed to identify the molecule that has a mass of 1481.6 Da. Major MS/MS peaks shown were best fitted to the masses of ion fragments of the 18TCLLIVFSK-6-TGDP adduct as follows: (i) 1462.8 Da, formed upon loss of H2O from the β-phosphate of the 6-TGDP moiety of 18TCLLIVFSK-6-TGDP adduct; (ii) 1445.6 Da., formed by losing an H2O and an OH from the β- and α-phosphate of the 6-TGDP moiety of 18TCLLIVFSK-6-TGDP adduct; (iii) 1400.4 Da, formed upon loss of COOH from the C terminus of the 18TCLLIVFSK-6-TGDP adduct as well as an H2O and an OH from the β- and α-phosphate of the 6-TGDP moiety of 18TCLLIVFSK-6-TGDP adduct; (iv) 1022.8 Da, formed upon loss of the 6-TGDP moiety from the 18TCLLIVFSK-6-TGDP adduct; and (v) the 978.3 Da, formed by losing the peptide C terminus COOH and the 6-TGDP moiety from the 18TCLLIVFSK-6-TGDP adduct.