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Updated: May 19, 2026
Generation of Native, Untagged Huntingtin Exon1 Monomer and Fibrils Using a SUMO Fusion Strategy
Published on: June 27, 2018
High yield expression of catalytically active USP18 (UBP43) using a Trigger Factor fusion system
Anja Basters1, Lars Ketscher, Elke Deuerling
1Department of Neuropathology, University of Freiburg, Freiburg, Germany.
Background:
Covalent linkage of the ubiquitin-like protein ISG15 interferes with viral infection and USP18 is the major protease which specifically removes ISG15 from target proteins. Thus, boosting ISG15 modification by protease inhibition of USP18 might represent a new strategy to interfere with viral replication. However, so far no heterologous expression system was available to yield sufficient amounts of catalytically active protein for high-throughput based inhibitor screens.
Results:
High-level heterologous expression of USP18 was achieved by applying a chaperone-based fusion system in E. coli. Pure protein was obtained in a single-step on IMAC via a His6-tag. The USP18 fusion protein exhibited enzymatic activity towards cell derived ISG15 conjugated substrates and efficiently hydrolyzed ISG15-AMC. Specificity towards ISG15 was shown by covalent adduct formation with ISG15 vinyl sulfone but not with ubiquitin vinyl sulfone.
Conclusion:
The results presented here show that a chaperone fusion system can provide high yields of proteins that are difficult to express. The USP18 protein obtained here is suited to setup high-throughput small molecule inhibitor screens and forms the basis for detailed biochemical and structural characterization.
