SOCS family proteins form part of a classical negative feedback system that regulates cytokine signal transduction. Substrate-recognition component of a SCF-like ECS (Elongin BC-CUL2/5-SOCS-box protein) E3 ubiquitin-protein ligase complex which mediates the ubiquitination and subsequent proteasomal degradation of target proteins. Inhibits EGF signaling by mediating the degradation of the Tyr-phosphorylated EGF receptor/EGFR (By similarity). Protein modification; protein ubiquitination. The SOCS box domain mediates the interaction with the Elongin BC complex, an adapter module in different E3 ubiquitin ligase complexes.