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Structural basis of sugar-recognizing ubiquitin ligase
Tsunehiro Mizushima1, Takeshi Hirao, Yukiko Yoshida
1Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan.
Nature Structural & Molecular Biology
|March 3, 2004
Summary
SCF(Fbs1) is a ubiquitin ligase that binds high-mannose oligosaccharides. Structural studies reveal Fbs1 binds chitobiose via hydrogen bonds and hydrophobic interactions, facilitating N-glycoprotein ubiquitination.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biology
Background:
- SCF(Fbs1) is a ubiquitin ligase involved in endoplasmic reticulum (ER)-associated degradation.
- Fbs1, an F-box protein, recognizes high-mannose oligosaccharides, crucial for N-glycan binding.
Purpose of the Study:
- To elucidate the structural basis of Fbs1's interaction with N-glycans.
- To understand the molecular mechanism of chitobiose recognition by Fbs1.
Main Methods:
- X-ray crystallography was used to determine the structure of the Fbs1 sugar-binding domain (SBD) alone and complexed with chitobiose.
- Nuclear Magnetic Resonance (NMR) spectroscopy was employed to investigate interactions at the chitobiose-binding site.
Main Results:
- The crystal structure revealed the Fbs1 SBD as a ten-stranded antiparallel beta-sandwich.
- Fbs1 forms hydrogen bonds with chitobiose and utilizes a hydrophobic pocket for methyl group insertion.
- NMR data indicated interactions between residues near the binding site and outer carbohydrate branches.
Conclusions:
- Fbs1 specifically binds to the chitobiose core of N-glycans.
- This interaction is proposed to occur with unfolded N-glycoproteins, positioning the protein moiety for ubiquitination by E2 enzymes.