Design and characterization of an active site selective caspase-3 transnitrosating agent

The oxidative addition of nitric oxide (NO) to a thiol, S-nitrosation, is a focus of studies on cyclic guanosine monophosphate (cGMP)-independent NO signaling. S-Nitrosation of the catalytic cysteine of the Caspase proteases has important effects on Apoptosis and consequently has received attention. Here we report on a small molecule that can directly probe the effects of S-nitrosation on the Caspase cascade. This chemical tool is capable of permeating the mammalian cell membrane, selectively transnitrosating the Caspase-3 active site cysteine, and halting Apoptosis in cultured human T-cells. The efficacy of this reagent was compared with the commonly used reagent S-nitrosoglutathione and an esterified derivative.