title: E2s: structurally economical and functionally replete.
abstract: Ubiquitination is a post-translational modification pathway involved in myriad cellular regulation and disease pathways. The Ub (ubiquitin) transfer cascade requires three enzyme activities: a Ub-activating (E1) enzyme, a Ub-conjugating (E2) enzyme, and a Ub ligase (E3). Because the E2 is responsible both for E3 selection and substrate modification, E2s function at the heart of the Ub transfer pathway and are responsible for much of the diversity of Ub cellular signalling. There are currently over 90 three-dimensional structures for E2s, both alone and in complex with protein binding partners, providing a wealth of information regarding how E2s are recognized by a wide variety of proteins. In the present review, we describe the prototypical E2-E3 interface and discuss limitations of current methods to identify cognate E2-E3 partners. We present non-canonical E2-protein interactions and highlight the economy of E2s in their ability to facilitate many protein-protein interactions at nearly every surface on their relatively small and compact catalytic domain. Lastly, we compare the structures of conjugated E2~Ub species, their unique protein interactions and the mechanistic insights provided by species that are poised to transfer Ub.
authors.affiliation: Department of Biochemistry, University of Washington, Box 357350, Seattle, WA 98195-97350, USA.
authors.forename: Dawn M
authors.initials: DM
authors.lastname: Wenzel
authors.forename: Kate E
authors.initials: KE
authors.lastname: Stoll
authors.forename: Rachel E
authors.initials: RE
authors.lastname: Klevit
mesh_terms: D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D044763:Ubiquitin-Conjugating Enzymes / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism / Q000502:physiology; D054875:Ubiquitination
chemical_list: D044763:Ubiquitin-Conjugating Enzymes; D044767:Ubiquitin-Protein Ligases