IL-2Rbeta is a member of the class I cytokine receptor superfamily. It carries a cytokine-binding homology region, which is divided in two fibronectin type-III (FN-III) domains termed D1 and D2. Each domain contains seven beta-strands that form a sandwich of two antiparallel beta-sheets. The N-terminal D1 domain of IL-2Rbeta includes two highly conserved disulfide bridges. This entry describes D1 of the N-terminal region of IL2Rbeta.