title: Structural basis of substrate recognition and specificity in the N-end rule pathway.
abstract: The N-end rule links the half-life of a protein to the identity of its N-terminal residue. Destabilizing N-terminal residues are recognized by E3 ubiquitin ligases, termed N-recognins. A conserved structural domain called the UBR box is responsible for their specificity. Here we report the crystal structures of the UBR boxes of the human N-recognins UBR1 and UBR2, alone and in complex with an N-end rule peptide, Arg-Ile-Phe-Ser. These structures show that the UBR box adopts a previously undescribed fold stabilized through the binding of three zinc ions to form a binding pocket for type 1 N-degrons. NMR experiments reveal a preference for N-terminal arginine. Peptide binding is abrogated by N-terminal acetylation of the peptide or loss of the positive charge of the N-terminal residue. These results rationalize and refine the empirical rules for the classification of type 1 N-degrons. We also confirm that a missense mutation in UBR1 that is responsible for Johanson-Blizzard syndrome leads to UBR box unfolding and loss of function.
authors.affiliation: Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
authors.forename: Edna
authors.initials: E
authors.lastname: Matta-Camacho
authors.forename: Guennadi
authors.initials: G
authors.lastname: Kozlov
authors.forename: Flora F
authors.initials: FF
authors.lastname: Li
authors.forename: Kalle
authors.initials: K
authors.lastname: Gehring
mesh_terms: D000107:Acetylation; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D001665:Binding Sites; D018360:Crystallography, X-Ray; D010188:Exocrine Pancreatic Insufficiency / Q000235:genetics; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D009842:Oligopeptides / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D025941:Protein Interaction Mapping; D011499:Protein Processing, Post-Translational; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013577:Syndrome; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016335:Zinc Fingers / Q000502:physiology
chemical_list: D000596:Amino Acids; D009842:Oligopeptides; C113474:UBR1 protein, human; C499858:UBR2 protein, human; D044767:Ubiquitin-Protein Ligases