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Updated: Jan 11, 2026
NMR-Based Fragment Screening in a Minimum Sample but Maximum Automation Mode
Published on: June 4, 2021
Nuclear Magnetic Resonance-based fragment screen of the E3 ligase Fem-1 homolog B
Jade M Katinas1, Kangsa Amporndanai1, Ashley J Taylor1
1Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA.
Abstract:
Targeted protein degradation using PROTACs (PROteolysis TArgeting Chimeras) has emerged as a transformative therapeutic strategy, largely relying on a small number of E3 ubiquitin ligases such as CRBN and VHL. However, resistance, toxicity, and poor oral bioavailability limit the utility of PROTACs and highlight the need to expand the E3 ligase toolbox. Fem-1 homolog B (FEM1B) is a lesser-known E3 ligase that offers a promising alternative due to its broad expression and ability to recognize diverse degron motifs. Here, we describe the development of a stable construct of FEM1B, the results of a protein-observed NMR-based fragment screen using this construct, and the X-ray structures of some of the fragment hits when bound to the protein. From these results, new PROTACs utilizing FEM1B as the E3 ligase may be discovered, providing an alternative E3 ligase for targeted protein degradation.
Insights
Researchers explored Fem-1 homolog B (FEM1B) as a novel E3 ligase for targeted protein degradation. This study developed a stable FEM1B construct and identified initial fragment binders, paving the way for new PROTAC therapies.
Area of Science:
- Biochemistry
- Molecular Biology
- Drug Discovery
Background:
- Targeted protein degradation using Proteolysis Targeting Chimeras (PROTACs) is a promising therapeutic strategy.
- Current PROTAC development relies heavily on E3 ligases like CRBN and VHL, but limitations such as resistance and toxicity necessitate new E3 ligase options.
- Fem-1 homolog B (FEM1B) presents a potential alternative E3 ligase due to its broad expression and ability to recognize diverse degron motifs.
Purpose of the Study:
- To develop a stable construct of the FEM1B E3 ligase for further research.
- To identify potential binding fragments for FEM1B using fragment-based screening.
- To lay the groundwork for discovering novel PROTACs utilizing FEM1B.
Main Methods:
- Development of a stable expression construct for the FEM1B E3 ligase.
- Protein-observed NMR-based fragment screening utilizing the FEM1B construct.
- X-ray crystallography to determine the structures of fragment hits bound to FEM1B.
Main Results:
- A stable construct of FEM1B was successfully developed.
- A fragment screen identified several potential binders for FEM1B.
- X-ray structures revealed the binding modes of these fragments to FEM1B.
Conclusions:
- FEM1B is a viable alternative E3 ligase for targeted protein degradation.
- The identified fragments serve as starting points for designing novel FEM1B-based PROTACs.
- This research expands the E3 ligase toolbox for developing next-generation therapeutic agents.
