Figure 2. Effects of FK506 and S107 on FKBP12 dissociation from SR vesicles in the presence of GSH and GSSG.

(A) Representative immunoblot of SR vesicles not treated and treated with FK506. SR vesicles were incubated with 10 µM FK506 as described in Materials and Methods, followed by centrifugation to remove FK506 and dissociated FKBP12. (B and C) FKBP12 dissociation from SR vesicles in the presence of GSH and GSSG. Immunoblots of SR vesicles not treated with FK506 were incubated for 1 and 20 h at 24°C in 0.25 M KCl, 20 mM imidazole, pH 7.0, 50 µM free Ca²⁺, protease inhibitors, and the indicated concentrations and ratios (5 mM total glutathione) of GSH and GSSG in the absence and presence of 44 µM S107. Free FKBP12 was removed by centrifugation. Data were normalized to SR vesicles not incubated (gray bar, 0 min) and are the mean ± SEM of 4–5 experiments. *p<0.05 compared to SR vesicles at 0 min not treated with S107.