RAP AS A MOLECULAR CHAPERONE/ESCORT PROTEIN FOR LRP

低密度脂蛋白受体相关蛋白(LRP)是一个非常大的(60万kDa) 含有四个相关胞外结构域的单链蛋白 由多个(分别为2、8、10、11个)富含半胱氨酸的配体组成的旋转 绑定重复进行。LRP已成为一种独特的内吞受体，因为它 能够在结构和功能上结合和内吞许多 不同的配体。这些物质包括载脂蛋白E、2-巨球蛋白、tPA、 和尿激酶型纤溶酶原激活剂。一种39 kDa受体相关蛋白 (RAP)与细胞内LRP共纯化并阻断与LRP的配体结合 在试管中。本提案提供的初步数据表明， 不同的配体结合到LRP和LRP上的多个不同区域 RAP上的结合位点。此外，许多合成LRP和RAP的细胞 也要为受体合成配体，这可以防止正确的 如果它们与早期相关联，LRP的折叠。私家侦探假设说唱 在LRP的折叠和适当的运输中起到守护作用 通过结合它，防止过早地与配体结合。 人们建议用实验来阐明RAP的分子机制。 与LRP交互，通过解决其结构特征来探索RAP的结构特征 晶体结构，确定RAP作为折叠伴侣的作用 体内和体外方法，并确定RAP和LRP的转运 既是作为单个分子，也是作为相互作用的络合物。

The LDL receptor-related protein (LRP) is an extremely large (600,000 kDa) single chain protein with four related extracellular domains that are in turn composed of multiple (2, 8, 10, 11 respectively) cysteine-rich ligand binding repeats. LRP has emerged as a unique endocytic receptor due to its ability to bind and endocytose a number of structurally and functionally distinct ligands. These include apolipoprotein E, 2-macroglobulin, tPA, and urokinase-plasminogen activator. A 39kDa receptor-associated protein (RAP) co-purifies with intracellular LRP and blocks ligand binding to LRP in vitro. Preliminary data provided in this proposal demonstrate that the different ligands bind to multiple and distinct regions on LRP and LRP binding sites on RAP. In addition, many cells that synthesize LRP and RAP also synthesize ligands for the receptor, which can prevent the correct folding of LRP if they associate to early. The P.I. hypothesizes that RAP serves a chaperoning function in the folding and proper trafficking of LRP by binding it and preventing premature association with ligand. Experiments are proposed to elucidate the molecular mechanism by which RAP interacts with LRP, explore the structural features of RAP by solving its crystal structure, determine the role of RAP as a folding chaperone using in vivo and in vitro methods, and define the trafficking of RAP and LRP both as individual molecules and interacting complexes.