Structure of a peptide:N-glycanase-Rad23 complex:: Insight into the deglycosylation for denatured glycoproteins
Structure of a peptide:N-glycanase-Rad23 complex:: Insight into the deglycosylation for denatured glycoproteins
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DOI：
10.1073/pnas.0502082102
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发表时间：
2005-06-28
影响因子：
11.1
通讯作者：
Cho, YJ
中科院分区：
文献类型：
--
作者：
Lee, JH;Choi, JM;Cho, YJ
在真核生物中，在折叠和运输过程中，质量控制系统必须将错误折叠的蛋白质与正确折叠的蛋白质区分开来。酵母肽：n -糖聚糖酶（yPNGase）特异性地将细胞质中n -连接糖蛋白的变性形式去糖基化，并通过DNA修复蛋白yRad23与26S蛋白酶体形成复合物，从而协助蛋白酶体介导的糖蛋白降解。在这里，我们描述了yRad23 （yRad23XBD，残基238-309）复合物和ypngas -yRad23XBD复合物结合caspase抑制剂Z-VAD-fmk的yPNGase和xpc结合域的晶体结构。yPNGase由三个结构域组成，一个包含Cys-His-Asp三联体的核心结构域、一个zn结合结构域和一个rad23结合结构域。yPNGase的N端和c端螺旋都通过广泛的疏水相互作用与yRad23相互作用。yPNGase的活性位点位于由所有PNGase成员中保守残基形成的深裂缝中，三个糖分子结合在该裂缝上。结合突变分析的复杂结构表明，裂缝的壁阻止天然糖蛋白进入yPNGase的活性位点，而裂缝足够宽，可以容纳变性糖蛋白，从而解释了PNGase对变性底物的特异性。
In eukaryotes, misfolded proteins must be distinguished from correctly folded proteins during folding and transport processes by quality control systems. Yeast peptide:N-glycanase (yPNGase) specifically deglycosylates the denatured form of N-linked glycoproteins in the cytoplasm and assists proteasome-mediated glycoprotein degradation by forming a complex with 26S proteasome through DNA repair protein, yRad23. Here, we describe the crystal structures of a yPNGase and XPC-binding domain of yRad23 (yRad23XBD, residues 238-309) complex and of a yPNGase-yRad23XBD complex bound to a caspase inhibitor, Z-VAD-fmk. yPNGase is formed with three domains, a core domain containing a Cys-His-Asp triad, a Zn-binding domain, and a Rad23-binding domain. Both N- and C-terminal helices of yPNGase interact with yRad23 through extensive hydrophobic interactions. The active site of yPNGase is located in a deep cleft that is formed with residues conserved in all PNGase members, and three sugar molecules are bound to this cleft. Complex structures in conjunction with mutational analyses revealed that the walls of the cleft block access to the active site of yPNGase by native glycoprotein, whereas the cleft is sufficiently wide to accommodate denatured glycoprotein, thus explaining the specificity of PNGase for denatured substrates.