Casputin™ reagent (human), (recombinant)

It is a recombinant fusion protein, which comprises BIRs (Baculovirus IAP Repeats) 2 and 3 from human XIAP (X-linked Inhibitor of Apoptosis Protein) plus the linker preceding BIR2. It is a potent inhibitor of caspase-3 and caspase-7, but has little or no effect on the activities of recombinant caspases -1, -2, -6, -8 and -9. Caspase-10 (Mch-4) is only weakly inhibited. It has been reported that other fusion proteins, which include the XIAP BIR 2, are inhibitory to caspases 7 and 9, but not caspase-6. Structural studies of a complex between caspase-7 and the linker-BIR2 portion of XIAP indicate that it is part of the linker region that occupies the substrate-binding groove of the caspase. The linker may therefore be the essential element for caspase inhibition, while the BIR domain apparently functions as a regulatory element and the site of Smac/DIABLO binding. Used together with a sensitive caspase such as caspase-7 (SE-177), it may be useful in screening for agents which block inhibition of caspases by IAPs.