The suppressor of cytokine signalling (SOCS) box was first identified in the SH2-containing SOCS box family (cytokine-inducible SH2-containing protein, SOCS1-7) and is a 40-amino acid motif, which functions to recruit an E3 ubiquitin ligase complex consisting of the adapter proteins elongins B and C, Rbx2 and the scaffold protein Cullin5. The SOCS box is found in a diverse array of intracellular signalling molecules, many of which contain different protein interaction domains such as SPRY and WD40 domains, leucine and ankyrin repeats or other functional domains such as GTPases. In general, the SOCS box-containing proteins are thought to act as substrate-recognition modules to mediate the polyubiquitination and subsequent degradation of substrate proteins by the 26S proteasome.
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