Ferritin nor E. coli MBP contain DXXD motifs. In contrast, GrpE, NusA, and thioredoxin do contain potential cleavage sites, although an analysis of the structures of GrpE [19] and thioredoxin [20] reveal that the DXXD sequences are present in well-defined -helical secondary structures and are likely not accessible to the caspase-3 protease active site. Currently, no structural information is avail