英国剑桥大学分子生物学医学研究委员会实验室David Komander研究组，引入Ub-clipping作为泛素链架构研究的新方法。相关论文发表在2019年8月15日出版的《自然》杂志上。

据介绍，其研究组引入Ub-clipping作为一种可以了解多聚泛素信号和架构的方法。Ub-clipping利用工程化的病毒蛋白酶Lb^pro∗从底物中不完全去除泛素，并将标记的C末端GlyGly二肽与修饰的残基连接；这简化了对底物和多聚泛蛋白内的蛋白质泛素化的直接评估。由Lb^pro∗产生的单泛蛋白保留了GlyGly修饰的残基，从而能够定量多重GlyGly修饰的分支点泛素蛋白。值得注意的是，他们发现聚合物中大量（10-20%）的泛素蛋白似乎以支链的形式存在。此外，Ub-clipping能够评估共存的泛素修饰。对去极化线粒体的分析揭示PINK1/parkin介导的线粒体自噬主要利用单链和短链多聚泛素化，其中磷酸化的泛素基团未被进一步修饰。因此，Ub-clipping这一方法可以促进对泛素密码的组合复杂性和体系结构的深入了解。

研究人员表示，蛋白质泛素化是一种多功能的翻译后修饰，影响所有的细胞过程。其多功能性源于结构复杂的多聚泛素链，其中单个泛素蛋白基团可在一个或多个残基上泛素化，和/或通过磷酸化和乙酰化修饰。质谱技术的进步使得能够绘制出泛素密码的各个泛素蛋白修饰；然而，多聚泛化信号的构架很大程度上还有待完善。

附：英文原文

Title: Insights into ubiquitin chain architecture using Ub-clipping

Author: Kirby N. Swatek, Joanne L. Usher, Anja F. Kueck, Christina Gladkova, Tycho E. T. Mevissen, Jonathan N. Pruneda, Tim Skern, David Komander

Issue&Volume: Volume 572 Issue 7770

Abstract: Protein ubiquitination is a multi-functional post-translational modification that affects all cellular processes. Its versatility arises from architecturally complex polyubiquitin chains, in which individual ubiquitin moieties may be ubiquitinated on one or multiple residues, and/or modified by phosphorylation and acetylation13. Advances in mass spectrometry have enabled the mapping of individual ubiquitin modifications that generate the ubiquitin code; however, the architecture of polyubiquitin signals has remained largely inaccessible. Here we introduce Ub-clipping as a methodology by which to understand polyubiquitin signals and architectures. Ub-clipping uses an engineered viral protease, Lbpro, to incompletely remove ubiquitin from substrates and leave the signature C-terminal GlyGly dipeptide attached to the modified residue; this simplifies the direct assessment of protein ubiquitination on substrates and within polyubiquitin. Monoubiquitin generated by Lbpro retains GlyGly-modified residues, enabling the quantification of multiply GlyGly-modified branch-point ubiquitin. Notably, we find that a large amount (1020%) of ubiquitin in polymers seems to exist as branched chains. Moreover, Ub-clipping enables the assessment of co-existing ubiquitin modifications. The analysis of depolarized mitochondria reveals that PINK1/parkin-mediated mitophagy predominantly exploits mono- and short-chain polyubiquitin, in which phosphorylated ubiquitin moieties are not further modified. Ub-clipping can therefore provide insight into the combinatorial complexity and architecture of the ubiquitin code.

DOI: 10.1038/s41586-019-1482-y

Source:https://www.nature.com/articles/s41586-019-1482-y