title: Structure of the HECT C-lobe of the UBR5 E3 ubiquitin ligase.
abstract: UBR5 ubiquitin ligase (also known as EDD, Rat100 or hHYD) is a member of the E3 protein family of HECT (homologous to E6-AP C-terminus) ligases as it contains a C-terminal HECT domain. In ubiquitination cascades involving E3s of the HECT class, ubiquitin is transferred from an associated E2 ubiquitin-conjugating enzyme to the acceptor cysteine of the HECT domain, which consists of structurally distinct N- and C-lobes connected by a flexible linker. Here, the high-resolution crystal structure of the C-lobe of the HECT domain of human UBR5 is presented. The structure reveals important features that are unique compared with other HECT domains. In particular, a distinct four-residue insert in the second helix elongates this helix, resulting in a strikingly different orientation of the preceding loop. This protruding loop is likely to contribute to specificity towards the E2 ubiquitin-conjugating enzyme UBCH4, which is an important functional partner of UBR5. Ubiquitination assays showed that the C-lobe of UBR5 is able to form a thioester-linked E3-ubiquitin complex, although it does not physically interact with UBCH4 in NMR experiments. This study contributes to a better understanding of UBR5 ubiquitination activity.
authors.affiliation: Groupe de Recherche axé sur la Structure des Protéines, Department of Biochemistry, McGill University, Montreal, Quebec H3G 0B1, Canada.
authors.forename: Edna
authors.initials: E
authors.lastname: Matta-Camacho
authors.forename: Guennadi
authors.initials: G
authors.lastname: Kozlov
authors.forename: Marie
authors.initials: M
authors.lastname: Menade
authors.forename: Kalle
authors.initials: K
authors.lastname: Gehring
mesh_terms: D000595:Amino Acid Sequence; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry*
chemical_list: C117617:UBR5 protein, human; D044767:Ubiquitin-Protein Ligases