Solution structure of the ubiquitin-conjugating enzyme UbcH5B |
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Authors: | Houben Klaartje Dominguez Cyril van Schaik Frederik M A Timmers H Th Marc Bonvin Alexandre M J J Boelens Rolf |
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Affiliation: | Department of NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands. |
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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. |
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Keywords: | ubiquitination NMR automated NOE assignment backbone dynamics diffusion anisotropy |
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