... opposite face of the protein to the phosphotyrosine-binding site, so the PEST sequence isnot expected to interfere with phosphotyrosine bindingby the SH2 domain. Indeed, replacing the entire35-residue ... hydrophilic,contain a high proportion of proline, glutamic acid,serine and threonine residues, and do not containlysine, arginine or histidine. The X-ray structures ofseveral proteins containing PEST ... C-terminalsuppressor of cytokine signalling (SOCS) box. SOCS3 and the related pro-tein, cytokine-inducible SH2-containing protein, are unique among the SOCS family of proteins in containing a region of mostly...