Structure and function of proteasome biogenesis associated proteins 1 and 2

描述（由申请人提供）：调节细胞内蛋白通量是细胞代谢的关键组成部分，该过程中的缺陷与多种人类疾病有关，包括神经变性、囊性纤维化和癌症。在真核生物中，20S蛋白酶体在细胞质和细胞核中进行大部分蛋白质水解，在蛋白质质量控制、信号转导、细胞周期进程、DNA修复和抗原递呈等多种过程中起着至关重要的作用。双对称的真核20S由28个（14 × 2）亚基组成，形成约730 kDa。桶状结构，包含6个蛋白水解位点。复杂的结构使得真核20S无法进行自组装。最近，一种异二聚体蛋白酶体相关生物发生因子（酵母中的Pba1/2；哺乳动物中的PAC1/2）被发现作为20S组装伴侣。有趣的是，Pba1/2还含有一个c端HbYX序列，这是一个已建立的20S激活基序，我们的初步数据显示Pba1/2与组装好的20S蛋白酶体结合。我们的主要目标是确定20S-Pba1/2相互作用的结构基础，为了实现这一目标，我们结晶了Pba1/2-20S配合物，并收集了3.0E分辨率的x射线衍射数据。我们将利用即将到来的结构信息来指导酵母中Pba1/2-20S相互作用的功能重要性的遗传和生化研究。我们还将确定Pba1/2是否与20S组装中间体相互作用，例如1-亚基的子集和其他伴侣。成功的结果将提供对蛋白酶体功能的结构和功能的了解，特别是Pba1/2。

DESCRIPTION (provided by applicant): Regulating intracellular protein flux is a critical component of cellular metabolism and defects in this process are linked to multiple human diseases including neurodegeneration, cystic fibrosis, and cancers. In eukaryotes, the 20S proteasome performs the bulk of proteolysis in the cytosol and nucleus and is vital in diverse processes such as protein quality control, signal transduction, cell cycle progression, DNA repair, and antigen presentation. The two-fold symmetric eukaryotic 20S is composed of 28 (14 x 2) subunits that form a ~730 kDa. barrel-like structure, which contains the six proteolytic sites. The complicated architecture renders eukaryotic 20S incapable of self-assembly. Recently, a heterodimeric Proteasome Associated Biogenesis factor (Pba1/2 in yeast; PAC1/2 in mammals) has been discovered that acts as a 20S assembly chaperone. Interestingly, Pba1/2 also contains a C-terminal HbYX sequence, which is an established 20S activating motif, and our preliminary data show that Pba1/2 binds to the assembled 20S proteasome. Our primary objective is to determine the structural basis for the 20S-Pba1/2 interaction, and toward this goal we have crystallized a Pba1/2-20S complex and collected X-ray diffraction data to 3.0E resolution. We will use the forthcoming structural information to guide genetic and biochemical investigations into the functional importance of Pba1/2-20S interactions in yeast. We will also determine if Pba1/2 interacts with 20S assembly intermediates, such as subsets of 1-subunits and other chaperones. Successful outcome will provide structural and functional insight into proteasome function in general and Pba1/2 in particular.