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SOCS (suppressors of cytokine signaling) box of SSB2 (SPRY domain-containing SOCS box proteins)-like proteins. SSB proteins contain a central SPRY domain and a C-terminal SOCS. SSB2 has been shown to bind to MET, the receptor protein-tyrosine kinase for hepatocyte growth factor (HGF). SSB2, like SSB4 and SSB1, also interacts with prostate apoptosis response protein-4. Both types of interactions are mediated through the SPRY domain. The general function of the SOCS box is the recruitment of the ubiquitin-transferase system. The SOCS box interacts with Elongins B and C, Cullin-5 or Cullin-2, Rbx-1, and E2. Therefore, SOCS-box-containing proteins probably function as E3 ubiquitin ligases and mediate the degradation of proteins associated through their N-terminal regions.