Plant E3 ligases: flexible enzymes in a sessile world.

E3 ligases comprise a highly diverse and important group of enzymes that act within the 26S ubiquitin proteasome pathway. They facilitate the transfer of ubiquitin moieties to substrate proteins which may be marked for degradation by this step. As such, they serve as central regulators in many cellular and physiological processes in plants. The review provides an update on the multitude of different E3 ligases currently known in plants, and illustrates the central role in plant biology of specific examples.