Probing ubiquitin topology

泛素是一种微小的蛋白质，存在于酵母和人类等多种生物体中。它负责调节细胞内的一系列过程，包括靶向破坏蛋白质、基因转录、细胞信号传导和控制通过细胞膜的交通。泛素通过一组酶的作用附着在靶蛋白上的一个或多个位点上，这一过程被称为泛素化。泛素与靶蛋白结构中的氨基酸赖氨酸偶联，由于泛素本身含有赖氨酸残基，因此泛素化过程中/通过7种赖氨酸中的任何一种连接，聚合泛素链都有可能建立起来。因此，多泛素可以根据其连接模式形成确定的形状或拓扑结构。人们认为，不同的拓扑结构和链长度可能对细胞内不同的功能负责，但探测多泛素链的完整拓扑结构以前是不可能的。在这里，我们提出了绘制多泛素连锁的方法，并确定了不同拓扑结构与泛素相互作用蛋白的结合，从而使我们能够解决“多泛素的形状和大小重要吗？”在一些重要的生物过程中。

Ubiquitin is a small protein found in organisms as diverse as yeast and man. It is responsible for the regulation of a host of processes within the cell, including targeting proteins for destruction, gene transcription, cell signalling, and controlling traffic through the cell membrane. Ubiquitin is attached to one or more sites on a target protein by the action of a set of enzymes in a process known as ubiquitination. Ubiquitin is coupled to the amino acid lysine within the target protein structure and, because ubiquitin itself contains lysine residues, it is possible for polymeric ubiquitin chains to build up during ubiquitination / through linkage at any of seven lysines. Thus, poly-ubiquitin can form defined shapes, or topologies, depending upon its linkage pattern. It is believed that different topologies and chain lengths maybe responsible for different functions within the cell, but probing the complete topology of a poly-ubiquitin chain has not previously been possible. Here we propose methods to map poly-ubiquitin linkage, and determine the binding of different topologies with ubiquitin-interacting proteins to allow us to tackle the key question 'does poly-ubiquitin shape and size matter?' in the context of some important biological processes.