The small ubiquitin-like modifier (SUMO) polypeptide that becomes covalently attached to various intracellular protein targets, much like ubiquitination, leading to post-translational modification of those targets. The surprising finding that plants have dedicated enzymes for chain synthesis implies a specific role for SUMO chains in plants. By the cooperative action with SUMO chain recognizing ubiquitin ligases, chains might channel substrates into the ubiquitin-dependent degradation pathway.
