Schematic representations of SOCS3 and three mutants with distinct functional domains deleted. The SOCS3 protein is structurally characterized by three distinct functional domains that include a N-terminal kinase inhibitory region (white), a central SH2 domain (black) and a C-terminal homologous region SOCS-box (gray). (a) The SOCS3-SH2 mutant is a full length SOCS3 without the SH2 region, consisting of the KIR and SOCS-box domains. (b) The KIR region is knocked out in the SOCS3-KIR mutant, with the SH2 and SOCS-box domains remained. (c) The SOCS-box mutant contains the SH2 and KIR domains, with the SOCS-box deleted. A myc tag was added to each of these SOCS3 mutants, and exogenous SOCS3 mutants were represented by the detection of myc tag.