title: Solution structure of the ubiquitin-conjugating enzyme UbcH5B.
abstract: The ubiquitination pathway is the main pathway for protein degradation in eukaryotic cells. The attachment of ubiquitin to a substrate protein is catalyzed by three types of enzymes, namely a ubiquitin activating enzyme (E1), a ubiquitin-conjugating enzyme (E2), and a ubiquitin ligase (E3). Here, the structure of the human ubiquitin-conjugating enzyme (E2) UbcH5B has been solved by a combination of homology modeling, NMR relaxation data and automated NOE assignments. Comparison to E2 structures solved previously by X-ray crystallography or NMR shows in all cases the same compact fold, but differences are observed in the orientation of both N and C-terminal alpha-helices. The N-terminal helix that is involved in binding to ubiquitin ligases (E3) displays a different position, which could have consequences for precise E2-E3 recognition. In addition, multiple conformations of the side-chain of Asn77 are found in solution, which contrasts the single hydrogen-bonded conformation in the crystal structures of E2 enzymes. The possible implication of this conformational freedom of Asn77 for its catalytic function is discussed.
authors.affiliation: Department of NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
authors.forename: Klaartje
authors.initials: K
authors.lastname: Houben
authors.forename: Cyril
authors.initials: C
authors.lastname: Dominguez
authors.forename: Frederik M A
authors.initials: FM
authors.lastname: van Schaik
authors.forename: H Th Marc
authors.initials: HT
authors.lastname: Timmers
authors.forename: Alexandre M J J
authors.initials: AM
authors.lastname: Bonvin
authors.forename: Rolf
authors.initials: R
authors.lastname: Boelens
mesh_terms: D000595:Amino Acid Sequence; D016880:Anisotropy; D001216:Asparagine / Q000737:chemistry; D017124:Conserved Sequence; D006801:Humans; D006860:Hydrogen Bonding; D008025:Ligases / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D012996:Solutions; D013059:Spectrum Analysis, Raman; D025801:Ubiquitin / Q000737:chemistry* / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D012996:Solutions; D025801:Ubiquitin; D001216:Asparagine; C097309:UBE2D2 protein, human; D044763:Ubiquitin-Conjugating Enzymes; D008025:Ligases