Figure 6.
Functional classification of linear motifs. Linear motifs can be divided into two major families, which each have three further subgroups. The modification class motifs all act as recognition sites for enzyme active sites, whereas the ligand class motifs are always recognized by the binding surface of a protein partner. More detailed classification beyond the graph shown here is possible. For example, an important subgroup of docking motifs are the degrons, which regulate protein stability by recruiting members of the ubiquitin–proteasome system. In the regular expressions, x corresponds to any amino acid, while other letters represent single letter codes of amino acids; letters within square brackets mean either residue is allowed in that position.