Hijacking the host ubiquitin pathway: structural strategies of bacterial E3 ubiquitin ligases

Ubiquitinylation of proteins is a critical mechanism in regulating numerous eukaryotic cellular processes including cell cycle progression, inflammatory response, and vesicular trafficking. Given the importance of ubiquitinylation, it is not surprising that several pathogenic bacteria have developed strategies to exploit various stages of the ubiquitin pathway for their own benefit. One such strategy is the delivery of bacterial ‘effector’ proteins into the host cell cytosol, which mimic the activities of components of the host ubiquitin pathway. Recent studies have highlighted a number of bacterial effectors that functionally mimic the activity of eukaryotic E3 ubiquitin ligases, including a novel structural class of bacterial E3 ligases that provides a striking example of convergent evolution.