Crystal Structure of RAIDD Death Domain Implicates Potential Mechanism of PIDDosome Assembly

Caspase-2 is implicated in stress-induced apoptosis that acts as an upstream initiator of mitochondrial permeabilization. Recent studies have shown that caspase-2 activation requires a molecular complex known as the PIDDosome comprising the p53-inducible protein PIDD, the adapter protein RAIDD and caspase-2. RAIDD has an N-terminal caspase recruitment domain (CARD) that interacts with the CARD of caspase-2 and a C-terminal death domain (DD) that interacts with the DD in PIDD. As a first step towards elucidating the molecular mechanisms of caspase-2 activation, we report the crystal structure of RAIDD DD at 2.0 Å resolution. The high-resolution structure reveals important features of RAIDD DD that may be important for DD folding and dynamics and for assembly of the PIDDosome.