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Updated: Aug 11, 2026
07:11
Constructing Cyclic Peptides Using an On-Tether Sulfonium Center
Published on: September 28, 2022
Chemical and Enzymatic Approaches to C-Terminal Cyclic Imide Formation
Zhenguang Zhao1, Ethan Yang Feng1, Wenqing Xu1
1Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, USA.
Methods in Molecular Biology (Clifton, N.J.)
|August 10, 2026
Summary
This study introduces new methods to create and detect C-terminal cyclic imide modifications, which are crucial for understanding how cereblon (CRBN) targets proteins for degradation.
Area of Science:
- Biochemistry and Molecular Biology
- Chemical Biology
- Proteomics
Background:
- The C-terminal cyclic imide modification serves as a degron, recognized by the E3 ligase adapter cereblon (CRBN).
- Understanding the biological roles of this modification necessitates reliable methods for its generation and detection on CRBN substrates.
Purpose of the Study:
- To describe practical protocols for producing C-terminal cyclic imide-modified peptides and proteins.
- To present analytical strategies for measuring substrate binding to CRBN and confirming modification formation.
Main Methods:
- Sortase-mediated transpeptidation for peptide and protein modification.
- Enzymatic conversion using protein carboxymethyltransferase (PCMT1).
- Time-resolved Förster resonance energy transfer (TR-FRET) assay for CRBN-substrate binding.
- Mass spectrometry for confirmation of cyclic imide formation.
Main Results:
- Successful implementation of two complementary methods for generating C-terminal cyclic imide modifications.
- Development of robust analytical techniques, including TR-FRET and mass spectrometry, for characterization.
- Demonstration of practical utility for investigating the chemistry and biology of these modifications.
Conclusions:
- The described protocols offer essential tools for researchers studying C-terminal cyclic imides and their interaction with CRBN.
- These methods facilitate deeper investigation into the biological significance of CRBN-mediated protein degradation pathways.
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