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C-terminal domain of Retinoic acid-inducible gene (RIG)-I protein, a cytoplasmic viral RNA receptor Retinoic acid-inducible gene (RIG)-I protein, also called DEAD box protein 58 (DDX58), is one of three members of the RIG-I-like Receptor (RLR) family. RLRs are cytoplasmic RNA receptors that recognize non-self RNA and act as molecular sensors to detect viral pathogens. RIG-I is activated by blunt-ended double-stranded RNA with or without a 5'-triphosphate (ppp), by single-stranded RNA marked by a 5'-ppp and by polyuridine sequences. It has been found to confer resistance to many negative-sense RNA viruses, including orthomyxoviruses, rhabdoviruses, bunyaviruses, and paramyxoviruses, as well as the positive-strand hepatitis C virus. RLRs are characterized by a central DExD/H-box helicase domain and a C-terminal domain, both of which are responsible for binding viral RNA. The helicase domain catalyzes the unwinding of double stranded RNA in an ATP-dependent manner. RIG-I and MDA5 also contain two N-terminal caspase activation and recruitment domains (CARDs), which initiate downstream signaling upon viral RNA sensing.
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