Molecular mechanism of substrate recognition of the ubiquitin-ligases that recognize sugar chain

识别糖链的泛素连接酶底物识别的分子机制

基本信息

批准号：
15580085
负责人：
YOSHIDA Yukiko
金额：
$ 2.37万
依托单位：
TOKYO MRTROPOLITAN ORGANIZATION FOR MEDICAL RESEARCH
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15580085/
关键词：
N-glycan Ubiquitin-ligase Lectin Endoplasmic reticulum associated degaradation (ERAD)

项目摘要

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.

为了寻找N-聚糖的新生物学功能，我们筛选了与各种糖问题结合的蛋白质的小鼠脑提取物，并发现FBX2一种F-box蛋白，与N-链接的高甘露糖型寡糖相连的蛋白质结合，随后有助于N-葡萄蛋白的蛋白质。我们提出SCF^<fbx2> Ubiquitylaltes N-糖基化蛋白，通过质量控制机制将其从ER转移到胞质溶胶。在这项研究中，我们发现了另一种识别N-聚糖的F-box蛋白FBS6B。 FBX2和FBX6B都与含有高曼诺糖寡糖的糖蛋白相互作用，其蛋白质修饰发生在ER中。 FBX2的底物结合结构域的X射线晶体学和核磁共振（NMR）研究表明，FBX2通过位于β-巴勒的顶部的小疏水袋识别出高甘露糖寡糖的内壳壳。 FBX2和FBX6B蛋白都与变性的糖蛋白相互作用，它们不仅用高甘露糖，而且还用复杂型寡糖修饰，比天然蛋白更有效。鉴于FBS蛋白与N-聚糖中的最内膜相互作用，我们建议FBS蛋白通过感测裸露的切托比索结构来区分天然与展开的糖蛋白。