Diagram illustrating domain structure and features of RIG-I, MDA5, and LGP2. The three RLRs are composed of a central DECH-box Helicase domain that encompasses conserved helicase subdomains, Hel1 (surrounding helicase motifs Q, I, II, and III) and Hel2 (surrounding helicase motifs IV, V, and VI). Between them lies the helicase insert domain, Hel2i. A C-terminal domain (CTD) is required for auto-regulation and RNA terminus recognition by RIG-I and shares some similarity with MDA5 and LGP2. RIG-I and MDA5 contain tandem caspase activation and recruitment domain (CARD) regions at their N-termini, which are essential for interactions with MAVS to promote downstream signaling.