126Gln is the residue of human IL-2 binding to IL-2R γ subunit

The 126Gln of human interleukin-2 (IL-2) is a conserved amino acid residue. After substitution of 126Gln with Asp, the binding abilities of this mutant to different composites of IL-2 receptor (R) subunits have been determined. Results show that 126Asp-IL-2 has higher affinity to IL-2R α βγ complex and normal affinity to IL-2R α β complex, but loses its binding ability to IL-2R β γ complex, demonstrating that the 126Gln is the residue of human IL-2 which binds to IL-2R 7 subunit.