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PDBsum entry 6fyh
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References listed in PDB file
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Key reference
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Title
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β-Sheet augmentation is a conserved mechanism of priming hect e3 ligases for ubiquitin ligation.
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Authors
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M.Jäckl,
C.Stollmaier,
T.Strohäker,
K.Hyz,
E.Maspero,
S.Polo,
S.Wiesner.
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Ref.
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J Mol Biol, 2018,
430,
3218-3233.
[DOI no: ]
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PubMed id
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Abstract
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Ubiquitin (Ub) ligases (E3s) catalyze the attachment of Ub chains to target
proteins and thereby regulate a wide array of signal transduction pathways in
eukaryotes. In HECT-type E3s, Ub first forms a thioester intermediate with a
strictly conserved Cys in the C-lobe of the HECT domain and is then ligated via
an isopeptide bond to a Lys residue in the substrate or a preceding Ub in a
poly-Ub chain. To date, many key aspects of HECT-mediated Ub transfer have
remained elusive. Here, we provide structural and functional insights into the
catalytic mechanism of the HECT-type ligase Huwe1 and compare it to the
unrelated, K63-specific Smurf2 E3, a member of the Nedd4 family. We found that
the Huwe1 HECT domain, in contrast to Nedd4-family E3s, prioritizes K6- and
K48-poly-Ub chains and does not interact with Ub in a non-covalent manner.
Despite these mechanistic differences, we demonstrate that the architecture of
the C-lobe~Ub intermediate is conserved between Huwe1 and Smurf2 and involves a
reorientation of the very C-terminal residues. Moreover, in Nedd4 E3s and Huwe1,
the individual sequence composition of the Huwe1 C-terminal tail modulates
ubiquitination activity, without affecting thioester formation. In sum, our data
suggest that catalysis of HECT ligases hold common features, such as the
β-sheet augmentation that primes the enzymes for ligation, and variable
elements, such as the sequence of the HECT C-terminal tail, that fine-tune
ubiquitination activity and may aid in determining Ub chain specificity by
positioning the substrate or acceptor Ub.
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