(A) An intramolecular interaction exists in Casp8 molecule. GST, GST-AR (1–36), GST-Casp8 (1–49), or GST-Casp8 (1–49/F45A) mutant was immobilized on glutathione-Sepharose beads and incubated with 35S-labeled Casp8 (1–100), Casp8 (1–150), Casp8 (1–200), or Casp8 (150–200) as indicated. After being washed, the beads were submitted to SDS–PAGE and the gel was analyzed by autoradiography. The input (IP) (5%) for the interaction assay was loaded onto the same gel. (B) Diagram of Casp8–AR interactions. Black boxes represent motifs that mediate Casp8–AR interactions.