 The Cdc4 substrate recognition mechanism includes the interaction with consensus binding motifs on the surface of the folded and phosphorylated Sic1, the so-called Cdc4 phospho-degrons (CPD).It has been shown that the optimal consensus sequence for Cdc4 is a phosphorylated serine or threonine followed by a proline and a basic amino acid.However, none of the CPDs on the surface of the Sic1 show such a composition.