The proteasome, the most complex protease known, degrades proteins that have been conjugated to ubiquitin. It faces the unique challenge of acting enzymatically on hundreds and perhaps thousands of structurally diverse substrates, mechanically unfolding them from their native state and translocating them vectorially from one specialized compartment of the enzyme to another. Moreover, substrates are modified by ubiquitin in myriad configurations of chains. The many unusual design features of the proteasome may have evolved in part to endow this enzyme with a robust ability to process substrates regardless of their identity. The proteasome plays a major role in preserving protein homeostasis in the cell, which requires adaptation to a wide variety of stress conditions. Modulation of proteasome function is achieved through a large network of proteins that interact with it dynamically, modify it enzymatically, or fine-tune its levels. The resulting adaptability of the proteasome, which is unique among proteases, enables cells to control the output of the ubiquitin-proteasome pathway on a global scale.

中文翻译：

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蛋白酶体及其网络：适应性工程。

蛋白酶体是已知的最复杂的蛋白酶，可降解与泛素结合的蛋白质。它面临着独特的挑战，即以酶促作用作用于成百上千种结构不同的底物，将它们从天然状态机械展开，并将它们从酶的一个专门区室以矢量方式转移到另一个区室。此外，底物在无数链结构中被泛素修饰。蛋白酶体的许多不同寻常的设计特征可能在一定程度上已经演变为赋予这种酶强大的处理底物的能力，而不管底物的身份如何。蛋白酶体在维持细胞内蛋白质稳态方面发挥着重要作用，这需要适应各种压力条件。蛋白酶体功能的调节是通过一个大型蛋白质网络实现的，这些蛋白质与其动态相互作用、酶促修饰或微调其水平。由此产生的蛋白酶体适应性，在蛋白酶中是独一无二的，使细胞能够在全球范围内控制泛素-蛋白酶体途径的输出。