In C. elegans, Ced4 binds and activates Ced3, an apoptotic initiator caspase, via caspase-associated recruitment domains (CARDs). Human Ced4 homologs include APAF1, NOD1, and NOD2. These proteins have at least 1 N-terminal CARD domain followed by a centrally located nucleotide-binding domain (NBD or NACHT) and a C-terminal regulatory domain, found only in mammals, that contains either WD40 repeats or leucine-rich repeats (LRRs). CARD12 is a member of the Ced4 family and can induce apoptosis.