PROTEASOME (26S PROTEASOME)

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得主要资金， 因此可以在其他CRISP条目中表示。列出的机构是 中心，不一定是研究者的机构。 蛋白酶体是存在于所有真核生物和古细菌以及某些细菌中的大型动态蛋白质复合物。蛋白酶体的主要功能是通过以ATP依赖性方式破坏肽键来降解错误折叠或受损的蛋白质。聚合的泛素链作为降解信号，将靶蛋白携带到蛋白酶体，在蛋白酶体中底物被蛋白水解分解。蛋白酶体是细胞调节特定蛋白质浓度和降解错误折叠蛋白质的主要机制的一部分。降解过程产生约7至8个氨基酸长的肽，然后可以进一步降解为氨基酸并用于合成新的蛋白质。泛素-蛋白酶体降解途径是许多细胞过程所必需的，包括细胞周期调节、DNA修复、凋亡、信号转导和蛋白质质量控制。 我们将用单粒子冷冻电镜观察牛26 S蛋白酶体的结构。本研究的具体目标是：1）在亚纳米分辨率下求解和比较单帽26 S蛋白酶体和双帽30 S蛋白酶体的结构：2）比较20 S蛋白酶体的X射线结构和非加帽26 S蛋白酶体的冷冻电镜结构; 3）通过比较26 S和30 S的冷冻电镜结构与已知的20 S结构，进一步阐明26 S蛋白酶体的门打开机制，其中26 S和30 S的门打开机制与已知的20 S结构不同。环保持关闭以阻挡甚至未折叠的基片的自由进入。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Proteasomes are large dynamic protein complexes existing inside all eukaryotes and archaea, as well as in some bacteria. The major function of the proteasome is to degrade misfolded or damaged proteins by breaking peptide bonds in an ATP-dependent manner. The polymerized ubiquitin chain acts as a degradation signal that carries the target proteins to the proteasome, where the substrate is proteolytically broken down. Proteasomes are part of a major mechanism by which cells regulate the concentration of particular proteins and degrade misfolded proteins. The degradation process yields peptides of about seven to eight amino acids long, which can then be further degraded into amino acids and used in synthesizing new proteins. The ubiquitin-proteasome degradation pathway is essential for many cellular processes, including cell-cycle regulation, DNA repair, apoptosis, signal transduction, and protein quality control. We are going to examine the structures of Bovine 26S proteasomes by single-particle cryo-EM. The specific aims for this proposal are: 1) to solve and compare the structures of single-capped 26S proteasome and double-capped 30S proteasome at subnanometer resolution; 2) to compare the solution structure of non-capped 20S by cryo-EM with the X-ray structure of 20S; 3) to further elucidate the gate opening mechanism of the 26S proteasome by comparing the cryo-EM structures of 26S and 30S with the known structure(s) of 20S, in which the gate in ¿¿ ring(s) remains closed to block the free entry of even unfolded substrates.