Protein folding in the endoplasmic reticulum

膜和分泌蛋白通过由内质网（ER）、高尔基体和分泌囊泡组成的分泌途径获得翻译后修饰并折叠。为了实现这一目标，细胞进化出一套专门的伴侣、酶和受体分子，介导蛋白质折叠和运输的多个步骤。**我的研究涉及内质网中蛋白质折叠的两个方面：1)n -连接糖蛋白的碳水化合物结构与伴侣蛋白募集之间的联系，以及2)未折叠蛋白质的识别机制。这两个过程都是由钙连接素周期的伴侣进行的。calnexin循环由折叠糖蛋白的伴侣蛋白和修饰附着的聚糖以反映蛋白质折叠状态的酶组成。这个循环的功能是促进新合成的糖蛋白的有效折叠，防止它们过早地从内质网输出。**关于calnexin周期有许多未解决的问题：i)伴侣在低等生物中是否有类似的功能？ii)钙连蛋白周期如何区分折叠蛋白和未折叠蛋白？iii)未折叠的蛋白质是如何被识别的，是否有一个通用的编码？我的研究小组在回答这些问题方面取得了重大进展。在已发表的工作中，我们发现了肽基脯氨酸异构酶与钙连联蛋白周期之间的一种新的关联。我们还确定了伴侣钙网蛋白如何识别聚糖。在未发表的工作中，我们从酵母中克隆、表达和纯化了calnexin循环成分和未折叠蛋白的关键内质网传感器。**在此，我建议将结构生物学和体外功能分析相结合，继续进行这些研究，重点研究两个目标：**1)酵母凝集素伴侣复合物的结构和功能研究。我们已经从酵母钙连蛋白（Cne1p）中鉴定出相互作用环，并表明它与酵母蛋白二硫异构酶（Mpd1p）相互作用。我们将识别bi

Membrane and secreted proteins acquire post-translational modifications and become folded through the secretory pathway comprised of the endoplasmic reticulum (ER), the Golgi body and secretory vesicles. To accomplish this, cells have evolved a set of specialized chaperones, enzymes, and receptor molecules that mediate the multiple steps of protein folding and trafficking. **My research addresses two aspects of protein folding in the ER: 1) the link between the carbohydrate structure of N-linked glycoproteins and the recruitment of chaperones, and 2) the mechanism of recognition of unfolded proteins. Both processes are carried out by chaperones of the calnexin cycle. The calnexin cycle consists of chaperones that fold glycoproteins and enzymes that modify the attached glycan to reflect the protein's folded state. The function of the cycle is to promote the efficient folding of newly synthesized glycoproteins and prevent their premature export from the ER.**There are a number of unanswered questions about the calnexin cycle: i) Do the chaperones function analogously in lower organisms? ii) How does the calnexin cycle distinguish between folded and unfolded proteins? iii) Is there a general code for how unfolded proteins are recognized? **My research group has made significant progress in answering these questions. In published work, we identified a novel association between a peptidyl prolyl isomerase and the calnexin cycle. We also determined how the chaperone calreticulin recognizes glycans. In unpublished work, we have cloned, expressed and purified calnexin cycle components from yeast and a key ER sensor of unfolded proteins. **Here, I propose to continue these studies by combining structural biology and in vitro functional assays with work focused on two aims:**1) Structural and functional studies of a lectin chaperone complex from yeast. We have identified the interaction loop from yeast calnexin (Cne1p) and shown that it interacts with a yeast protein disulfide isomerase (Mpd1p). We will identify the bi