Structures of the 1∶2 complexes.
(A) GH:(GHR)2. (B) EPO:(EPOR)2. (C) PRL:(PRLR)2. The cytokine (GH, EPO, or PRL) is in the middle in green; receptor 2 (R2) is on the left and receptor 1 (R1) is on the right. Each receptor ECD is composed of an N-terminal subdomain (N1 in purple and N2 in blue) and a C-terminal subdomain (C1 in orange and C2 in red).