Initiation of programmed cell death in C.elegans occurs by the binding of EGL-1 to CED-9 which disrupts a complex involving CED-4/CED-9 and allows CED-4 to activate CED-3, a caspase. It is the C terminal domain of EGL-1 which is involved in the formation of the complex with CED-9. The formation of the complex induces structural rearrangements in CED-9 and EGL-1 adopts an extended alpha-helical conformation [1].

1: Structural, biochemical, and functional analyses of CED-9 recognition by the proapoptotic proteins EGL-1 and CED-4. Yan N, Gu L, Kokel D, Chai J, Li W, Han A, Chen L, Xue D, Shi Y; Mol Cell. 2004;15:999-1006. PMID:15383288