RIG-I (retinoic-acid-inducible gene I), also known as DDX58 (DEAD (Asp-Glu-Ala-Asp) box polypeptide 58) is a 925-residue cytoplasmic viral RNA receptor, critically involved in the activation of the innate immune response to RNA virus infection. It is a member of the RIG-I-like receptor (RLR) family and is an essential intracellular sensor for several 5-triphosphorylated RNA viruses. RIG-I elicits its antiviral interferon (IFN) responses by recognizing viral double-stranded RNAs (dsRNAs). Structurally it comprises a helicase domain, a C-terminal domain, and N-terminal CARDs (caspase activation recruitment domains) involved in activating MAVS (mitochondrial antiviral signaling protein). Upon binding of 5-triphosphorylated RNA, RIG-I undergoes conformational changes and post-translational modifications that allow multimerization and interaction with the mitochondrial antiviral signaling protein (MAVS).