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Article Dans Une Revue Biochemical Journal Année : 2008

Biochemical function of typical and variant Arabidopsis thaliana U-box E3 ubiquitin-protein ligases

Jakob Wiborg
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Charlotte O'Shea
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Karen Skriver
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Résumé

The variance of the U-box domain in sixtyfour Arabidopsis thaliana ubiquitin-protein ligases (E3s) was used to examine the interactions between E3s and ubiquitin-conjugating enzymes (E2s). E2s and E3s are components of the ubiquitin protein degradation pathway. Seven U-box proteins were analyzed for their ability to ubiquitinate proteins in vitro in cooperation with different E2s. All U-box domains exhibited ubiquitination activity and interacted productively with UBC4/5-type E2s. Three and four of the U-box domains mediated ubiquitin addition in the presence of UBC13 and UBC7 E2s, respectively, but no productive interaction was observed with the UBC15 E2 tested. The activity of AtPUB54 was dependent on Trp266 in the E2-binding cleft, and the E2 selectivity was changed by substitution of this position. The function of the distant U-box protein, AtPUB49, representing a large family of eukaryotic proteins containing a U-box linked to a cyclophilin-like peptidyl-prolyl cis-trans isomerase domain, was characterized biochemically. AtPUB49 functioned both as a prolyl isomerase and a chaperone by catalyzing cis/trans isomerization of peptidyl-prolyl bonds and dissolving protein aggregates. In conclusion, both typical and atypical Arabidopsis U-box proteins were active E3s. The overlap in the E3/E2 selectivity suggests that in vivo specificity is not determined only by the E3/E2 interactions but also by other parameters, e.g. co-existence or interactions with additional domains. The biochemical functions of AtPUB49 suggest that the protein can be involved in folding or degradation of protein substrates. Similar functions can also be retained within a protein complex with separate chaperone and U-box proteins.

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Dates et versions

hal-00478916 , version 1 (30-04-2010)

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Jakob Wiborg, Charlotte O'Shea, Karen Skriver. Biochemical function of typical and variant Arabidopsis thaliana U-box E3 ubiquitin-protein ligases. Biochemical Journal, 2008, 413 (3), pp.447-457. ⟨10.1042/BJ20071568⟩. ⟨hal-00478916⟩

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