Glycan moieties are essential for folding, sorting and targeting of glycoproteins through the secretory pathway to various cellular compartments. The molecular mechanisms that underlie these processes, however, are only now coming to light. Recent crystallographic and NMR studies of proteins located in the endoplasmic reticulum (ER), Golgi complex and ER-Golgi intermediate compartment have illuminated their roles in glycoprotein folding and secretion. Calnexin and calreticulin, both ER-resident proteins, have lectin domains that are crucial for their function as chaperones. The crystal structure of the carbohydrate-recognition domain of ER-Golgi intermediate compartment (ERGIC)-53 complements the biochemical and functional characterization of the protein, confirming that a lectin domain is essential for the role of this protein in sorting and transfer of glycoproteins from the ER to the Golgi complex. The lectin domains of calnexin and ERGIC-53 are structurally similar, although there is little primary sequence similarity. By contrast, sequence similarity between ERGIC-53 and vesicular integral membrane protein (VIP36), a Golgi-resident protein, leaves little doubt that a similar lectin domain is central to the transport and/or sorting functions of VIP36. The theme emerging from these studies is that carbohydrate recognition and modification are central to mediation of glycoprotein folding and secretion.

中文翻译：

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凝集素控制分泌途径中蛋白质的折叠和分类。

聚糖部分对于糖蛋白的折叠，分选和靶向通过分泌途径到达各种细胞区室是必不可少的。然而，这些过程背后的分子机制才刚刚被发现。最近对位于内质网（ER），高尔基复合体和ER-高尔基体中间区室的蛋白质的晶体学和NMR研究证明了它们在糖蛋白折叠和分泌中的作用。钙结合蛋白和钙网蛋白都是内质网驻留蛋白，其凝集素结构域对于其作为伴侣蛋白的功能至关重要。ER-高尔基体中间区（ERGIC）-53的碳水化合物识别结构域的晶体结构补充了该蛋白质的生化和功能特征，证实凝集素结构域对该蛋白在糖蛋白从ER到高尔基复合体的分选和转移中的作用至关重要。钙粘蛋白和ERGIC-53的凝集素结构域在结构上相似，尽管基本序列相似性很小。相比之下，ERGIC-53与高尔基驻留蛋白水泡整合膜蛋白（VIP36）之间的序列相似性毫无疑问，类似的凝集素结构域对VIP36的转运和/或分选功能至关重要。这些研究的主题是碳水化合物的识别和修饰对于糖蛋白折叠和分泌的调节至关重要。ERGIC-53与高尔基驻留蛋白水泡整合膜蛋白（VIP36）之间的序列相似性毫无疑问，类似的凝集素结构域对VIP36的转运和/或分选功能至关重要。这些研究的主题是碳水化合物的识别和修饰对于糖蛋白折叠和分泌的调节至关重要。ERGIC-53与高尔基驻留蛋白水泡整合膜蛋白（VIP36）之间的序列相似性毫无疑问，类似的凝集素结构域对VIP36的转运和/或分选功能至关重要。这些研究的主题是碳水化合物的识别和修饰对于糖蛋白折叠和分泌的调节至关重要。