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Updated: May 18, 2026

In Vitro Analysis of E3 Ubiquitin Ligase Function
Published on: May 14, 2021
Mechanism-based small molecule cross-linkers of HECT E3 ubiquitin ligase-substrate pairs
Sungjin Park1, Ioanna Ntai, Paul Thomas
1Department of Chemistry, Center for Molecular Innovation and Drug Discovery, Proteomics Center of Excellence, Chemistry of Life Processes Institute, Northwestern University, Silverman Hall, 2145 Sheridan Road, Evanston, IL 60208, USA.
Abstract:
Here we report the discovery that bifunctional thiol- and amine-reactive electrophiles serve as mechanism-based covalent cross-linkers for HECT E3 ubiquitin ligase-substrate pairs. We demonstrate that these chemical cross-linkers covalently cross-link the catalytic Cys residue of the yeast HECT E3 ubiquitin ligase Rsp5 with the Lys of the ubiquitination site in the model substrate Sic60-GFP. This work represents the first example of a mechanism-based covalent cross-link of HECT E3-substrate pairs that converts transiently interacting HECT E3-substrate pairs into stable, covalently cross-linked protein complexes, thereby facilitating their subsequent isolation, identification, and study.
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