XIAP and brain ischemia: Taken together, in this study we find a new mechanism for procaspase-9 transnitrosylating XIAP: after cerebral ischemia-reperfusion, the NO group of procaspase-9 is first transferred to the free thiol of Cys32 of Trx1- (SH)2 and subsequently transferred to Cys73 intramolecularly to form SNO-Trx1-S2.