RIG-I is a protein that binds cytosolic viral RNA and ATP to trigger an immune response . In this study, we used the C268F variant of RIG-I that can trigger the immune response without ATP. The crystal structure of RIG-I consists of a protein of 922 residues (residues 1-239 and 823-925 not modeled) which surrounds two identical RNA chains of 13 nucleotides that are bound into a double helical structure. There is also one Zn and one Mg ion bound in the complex.