Protein folding in the endoplasmic reticulum

膜蛋白和分泌蛋白获得翻译后修饰，并通过由内质网（ER）、高尔基体和分泌囊泡组成的分泌途径折叠。为了实现这一点，细胞已经进化出一套专门的分子伴侣、酶和受体分子，它们介导蛋白质折叠和运输的多个步骤。 ** 我的研究涉及ER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分子伴侣的募集之间的联系，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蛋白循环的伴侣进行的。钙连接蛋白循环由折叠糖蛋白的分子伴侣和修饰所连接的聚糖以反映蛋白质折叠状态的酶组成。 该循环的功能是促进新合成的糖蛋白的有效折叠，并防止它们过早地从ER输出。关于钙连接蛋白循环有许多未回答的问题：i）伴侣蛋白在低等生物中是否具有类似的功能？ ii）钙连接蛋白循环如何区分折叠和未折叠的蛋白质？iii）对于如何识别未折叠的蛋白质，是否有一个通用代码？** 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，我们确定了一种新的肽基脯氨酰异构酶和钙连接蛋白循环之间的关联。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，我们已经克隆，表达和纯化了来自酵母的钙连接蛋白循环组分和未折叠蛋白的关键ER传感器。** 在这里，我建议通过结合结构生物学和体外功能测定来继续这些研究，工作集中在两个目标上：**1）酵母凝集素伴侣复合物的结构和功能研究。我们已经确定了酵母钙连接蛋白（Cne 1 p）的相互作用环，并表明它与酵母蛋白质二硫键异构酶（Mpd 1 p）相互作用。我们会找出

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 In unpublished work, we have cloned, expressed and purified calnexin cycle components from yeast and a key ER sensor of unfolded proteins.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