Moremen Kelley W, Molinari Maurizio
Complex Carbohydrate Research Center, University of Georgia, Athens, GA 30602-4712, USA.
Curr Opin Struct Biol. 2006 Oct;16(5):592-9. doi: 10.1016/j.sbi.2006.08.005. Epub 2006 Aug 30.
Nascent polypeptides emerging into the lumen of the endoplasmic reticulum (ER) are N-glycosylated on asparagines in Asn-Xxx-Ser/Thr motifs. Processing of the core oligosaccharide eventually determines the fate of the associated polypeptide by regulating entry into and retention by the calnexin chaperone system, or extraction from the ER folding environment for disposal. Recent advances have shown that at least two N-glycans are necessary for protein access to the calnexin chaperone system and that polypeptide cycling in the system is a rather rare event, which, for folding-defective polypeptides, is activated only upon persistent misfolding. Additionally, dismantling of the polypeptide-bound N-glycan interrupts futile folding attempts, and elicits preparation of the misfolded chain for dislocation into the cytosol and degradation.
进入内质网（ER）腔的新生多肽在Asn-Xxx-Ser/Thr基序中的天冬酰胺上进行N-糖基化。核心寡糖的加工最终通过调节进入钙连蛋白伴侣系统并被其保留，或从ER折叠环境中提取以进行处理，来决定相关多肽的命运。最近的进展表明，至少两个N-聚糖是蛋白质进入钙连蛋白伴侣系统所必需的，并且该系统中的多肽循环是一个相当罕见的事件，对于折叠缺陷的多肽，只有在持续错误折叠时才会被激活。此外，多肽结合的N-聚糖的拆解会中断徒劳的折叠尝试，并引发将错误折叠的链准备好错位到细胞质中并进行降解。
