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Skp1 Dimerization Conceals Its F-Box Protein Binding Site
Biochemistry
|April 2, 2020
Summary
Skp1 protein forms a dimer in solution but binds F-box proteins as a monomer. Disrupting the Skp1 dimer interface allows monomeric Skp1 to bind F-box proteins, suggesting dimerization is not essential for function.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biology
Background:
- Skp1 acts as a crucial adapter in SCF E3 ubiquitin ligase complexes, linking F-box proteins to cullin-1.
- Skp1 from Dictyostelium exhibits distinct oligomeric states: a stable homodimer in vitro and a monomer in crystal complexes with F-box proteins (FBPs).
Purpose of the Study:
- To elucidate the structural basis for Skp1's differential oligomerization states.
- To investigate how Skp1 dimerization influences its interaction with F-box proteins.
Main Methods:
- Solution Nuclear Magnetic Resonance (NMR) spectroscopy to determine the structure of a truncated Skp1 homodimer (Skp1ΔΔ).
- Computational modeling using Rosetta to predict interface-disrupting mutations.
- Biochemical assays to assess the binding of a modified Skp1 (Skp1ΔF97E) to an FBP.
Main Results:
- The solution NMR structure of Skp1ΔΔ revealed a homodimer with a 2-fold symmetric interface that overlaps with the F-box binding site.
- A predicted mutation (F97E) disrupted the dimer interface, yielding a monomeric Skp1 (Skp1ΔF97E).
- Monomeric Skp1ΔF97E actively bound a model F-box protein, demonstrating functional monomeric activity.
Conclusions:
- Skp1 dimerization sterically hinders F-box protein binding.
- The dimeric state of Skp1 is not essential for its fundamental biochemical function of binding F-box proteins.
- Skp1ΔF97E provides a monomeric model for future high-resolution structural studies.
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