2004 Fiscal Year Final Research Report Summary
Molecular mechanism of substrate recognition of the ubiquitin-ligases that recognize sugar chain
| Project/Area Number |
15580085
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied biochemistry
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| Research Institution | TOKYO MRTROPOLITAN ORGANIZATION FOR MEDICAL RESEARCH |
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Principal Investigator |
YOSHIDA Yukiko Tokyo Metropolitan Organization for Medical Research, Tokyo Metropolitan of Medical Science, Researcher, 東京都臨床医学総合研究所, 研究員 (90271543)
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| Project Period (FY) |
2003 – 2004
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| Keywords | N-glycan / Ubiquitin-ligase / Lectin / Endoplasmic reticulum associated degaradation (ERAD) |
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| Research Abstract |
In an attempt to find novel biological functions for N-glycans, we screened mouse brain extracts for proteins bound to various sugar probes, and found Fbx2 an F-box protein, binds specifically to proteins attached with N-linked high-mannose type oligosaccharides, and subsequently contributes to ubiquitylation of N-glycosylated proteins. We propose that SCF^<Fbx2> ubiquitylaltes N-glycosylated proteins, which are translocated from the ER to the cytosol by the quality control mechanism. In this study, we found another F-box protein, Fbs6b that recognize N-glycans. Both Fbx2 and Fbx6b interacted with glycoproteins containing high-mannose oligosaccharides, whose protein modification occurs in the ER. X-ray crystallographic and nuclear magnetic resonance (NMR) studies of the substrates-binding domain of Fbx2 revealed that Fbx2 recognized the inner chitobiose of high-mannose oligosaccharides by a small hydrophobic pocket located at the top of the β-barrel. Both Fbx2 and Fbx6b proteins interacted with denatured glycoproteins, which were modified with not only high-mannose but also complex-type oligosaccharides, more efficiently than native proteins. Given that Fbs proteins interact with innermost chitobiose in N-glycans, we propose that Fbs proteins distinguish native from unfolded glycoproteins by sensing the exposed chitobiose structure.
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