RIP (Receptor Interacting Protein) is a 74 kDa Ser/Thr kinase which interacts with CD95 (Fas/Apo1) receptor and the tumor necrosis factor receptor (TNFR1). It is a cell death domain adapter protein which can bind to the adapter proteins TRADD, RAID, and TRAF2. RIP contains an N-terminal region with homology to protein kinase, an intermediate domain capable of association with MAPKKK and a C-terminal region containing an intracellular death domain motif. RIP activates both p38 MAP kinase and SAPK families. In vitro, RIP induces apoptosis, as well as SAPK/JNK and NF-kB activation. RIP possesses kinase activity as it autophosphorylates itself on serine and threonine residues.