Crystal and solution structure of the human RIG-I SF2 domain.

RIG-I is a pathogen-recognition receptor that recognizes viral 5'-triphosphates carrying double-stranded RNA. Upon binding to these microbe-associated molecular patterns (MAMPs), RIG-I forms oligomers and promotes downstream processes that result in type I interferon production and induction of an antiviral state. Here, the crystal structure of the human RIG-I superfamily 2 ATPase domain crystallized in an unusually elongated and open conformation is reported. The elongated structure is probably induced in part by crystal packing, but nevertheless indicates that the domain is intrinsically very flexible. This flexibility might allow substantial structural changes upon substrate binding and oligomerization.