Fig. 2.

Sulfhydration is a physiologic posttranslational modification absent in CSE^−/− animals. (A) Measurements of H₂S production with an H₂S-selective electrode indicate that CSE^−/− liver cannot generate H₂S. All results are presented as the mean ± SEM. ***P < 0.001. (B) Modified biotin switch assay in liver shows the presence of endogenous physiologic sulfhydration of GAPDH, β-tubulin, and actin in wild-type but not CSE^−/− animals. (C) Densitometric analysis quantitating basal protein sulfhydration in liver. Data are the mean ± SEM for five to seven independent experiments with representative data shown in (B) and (D). (D) Modified biotin switch assay in liver lysates incubated with increasing exogenous doses of the CSE substrate L-cysteine for 30 min at 37°C shows a dose-dependent increase in sulfhydration in wild-type but not CSE^−/− animals. The untreated lanes represent endogenous liver sulfhydration, showing a substantially larger signal for GAPDH than for β-tubulin or actin, consistent with the mean values depicted in (C). (E) Densitometric analysis of (D) quantitating changes in GAPDH sulfhydration with increasing exogenous doses of L-cysteine. Data are the mean ± SEM for five to seven independent experiments.