Death Domain (DD) found in tumor necrosis factor receptor-1 (TNFR-1). TNFR-1 has many names including TNFRSF1A, CD120a, p55, p60, and TNFR60. It activates two major intracellular signaling pathways that lead to the activation of the transcription factor NF-kB and the induction of cell death. Upon binding of its ligand TNF, TNFR-1 trimerizes which leads to the recruitment of an adaptor protein named TNFR-associated death domain protein (TRADD) through a DD/DD interaction. Mutations in the TNFRSF1A gene causes TNFR-associated periodic syndrome (TRAPS), a rare disorder characterized recurrent fever, myalgia, abdominal pain, conjunctivitis and skin eruptions. DDs are protein-protein interaction domains found in a variety of domain architectures. Their common feature is that they form homodimers by self-association or heterodimers by associating with other members of the DD superfamily including CARD (Caspase activation and recruitment domain), DED (Death Effector Domain), and PYRIN. They serve as adaptors in signaling pathways and can recruit other proteins into signaling complexes.