Figure 6.

GST-DIAP1 inhibits the caspase activity of bacterially synthesized DCP-1³¹-His₆, but not drICE⁸¹-HIS₆. Purified GST-DIAP1 (0.16 μM) (open triangles) or GST (0.48 μM) (open squares) was incubated with a fixed amount of DCP-1³¹His₆ (0.2nM) in caspase activity assay buffer containing 100 μM of the Ac-DEVD-AFC substrate. Release of AFC was monitored fluorometrically over time. GST-DIAP1 inhibits DCP-1-dependent caspase activity (A). In similar experiments in which 0.62nM drICE⁸¹His₆ was incubated in caspase activity buffer with GST (0.48 μM) or GST-DIAP1, (0.16 μM), no inhibition of drICE activity by GST-DIAP1was seen (B).