title: The MLLE domain of the ubiquitin ligase UBR5 binds to its catalytic domain to regulate substrate binding.
abstract: E3 ubiquitin ligases catalyze the transfer of ubiquitin from an E2-conjugating enzyme to a substrate. UBR5, homologous to the E6AP C terminus (HECT)-type E3 ligase, mediates the ubiquitination of proteins involved in translation regulation, DNA damage response, and gluconeogenesis. In addition, UBR5 functions in a ligase-independent manner by prompting protein/protein interactions without ubiquitination of the binding partner. Despite recent functional studies, the mechanisms involved in substrate recognition and selective ubiquitination of its binding partners remain elusive. The C terminus of UBR5 harbors the HECT catalytic domain and an adjacent MLLE domain. MLLE domains mediate protein/protein interactions through the binding of a conserved peptide motif, termed PAM2. Here, we characterize the binding properties of the UBR5 MLLE domain to PAM2 peptides from Paip1 and GW182. The crystal structure with a Paip1 PAM2 peptide reveals the network of hydrophobic and ionic interactions that drive binding. In addition, we identify a novel interaction of the MLLE domain with the adjacent HECT domain mediated by a PAM2-like sequence. Our results confirm the role of the MLLE domain of UBR5 in substrate recruitment and suggest a potential role in regulating UBR5 ligase activity.
authors.affiliation: From the Department of Biochemistry, Groupe de Recherche Axé sur la Structure des Protéines, McGill University, Montréal, Québec H3G 0B1, Canada.
authors.forename: Juliana
authors.initials: J
authors.lastname: Muñoz-Escobar
authors.affiliation: From the Department of Biochemistry, Groupe de Recherche Axé sur la Structure des Protéines, McGill University, Montréal, Québec H3G 0B1, Canada.
authors.forename: Edna
authors.initials: E
authors.lastname: Matta-Camacho
authors.affiliation: From the Department of Biochemistry, Groupe de Recherche Axé sur la Structure des Protéines, McGill University, Montréal, Québec H3G 0B1, Canada.
authors.forename: Guennadi
authors.initials: G
authors.lastname: Kozlov
authors.affiliation: From the Department of Biochemistry, Groupe de Recherche Axé sur la Structure des Protéines, McGill University, Montréal, Québec H3G 0B1, Canada kalle.gehring@mcgill.ca.
authors.forename: Kalle
authors.initials: K
authors.lastname: Gehring
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D018360:Crystallography, X-Ray; D006801:Humans; D010448:Peptide Initiation Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010455:Peptides / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D051381:Rats; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: C111580:PAIP1 protein, human; D010448:Peptide Initiation Factors; D010455:Peptides; D016601:RNA-Binding Proteins; C117617:UBR5 protein, human; D044767:Ubiquitin-Protein Ligases
keywords: E3 ubiquitin ligase; UBR5; crystal structure; isothermal titration calorimetry; nuclear magnetic resonance (NMR); poly(A)-binding protein; protein domain; protein/protein interaction; structural biology; x-ray crystallography