Homology modeling study of the human interleukin-7 receptor complex

Following a recent model of human interleukin-7 (IL-7), we present here a modeling study of the extracellular part of the human IL-7 receptor complex, including the IL-7 specific (IL-7R) and the common gamma (gamma c) chains. The investigation is based on structural homology to the complex of human growth hormone (hGH) bound to its receptor (hGHR). For domain 1 of IL-7R two different models are presented which differ in the alignment to hGHR in three regions. However, these differences affect binding to IL-7 in only one region, at the interface between loop EF of domain 1 of IL-7R and helix C of IL-7. The disulfide pattern in domain 1 of IL-7R is predicted to deviate from that observed in hGHR in that the C'-E disulfide (hGHR) is replaced by a C-C' cross-link. The prediction for the gamma c chain is compared with two previous studies. The models of the complex provide insight into the binding of IL-7 to its receptor and have implications for the suggestion of mutagenesis experiments and the design of (ant)agonists.