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J Mol Biol. 2004 Nov 19;344(2):513-26.

Solution structure of the ubiquitin-conjugating enzyme UbcH5B.

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  • 1Department of NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.

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.

PMID:
15522302
[PubMed - indexed for MEDLINE]
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