“…15,19,21 In contrast, the three N-terminal domains of ifnar1 are required for binding of IFNs, 22,23 yet ifnar1 binds IFN ligands with affinities that are 2-3 orders of magnitude lower than that of ifnar2. 24 Mutational studies have corroborated the involvement of the three N-terminal Ig-like domains of ifnar1 in the interaction with the ligand, 25,26 which was also confirmed by a recent three-dimensional reconstruction of the ternary complex by a single-particle electron microscopic analysis. 27 The membraneproximal Ig-like domain is not required for ligand binding, but has very specific properties required for the assembly of the ternary complex on the plasma membrane.…”