Puvar Kedar, Zhou Yiyang, Qiu Jiazhang, Luo Zhao-Qing, Wirth Mary J, Das Chittaranjan
Department of Chemistry, Purdue University , 560 Oval Drive, West Lafayette, Indiana 47906, United States.
Purdue Institute of Immunology, Inflammation, and Infectious Diseases and Department of Biological Sciences, Purdue University , 915 West State Street, West Lafayette, Indiana 47906, United States.
Biochemistry. 2017 Sep 12;56(36):4762-4766. doi: 10.1021/acs.biochem.7b00664. Epub 2017 Aug 18.
The SidE family of Legionella pneumophila effectors is a unique group of ubiquitin-modifying enzymes. Along with catalyzing NAD-dependent ubiquitination of certain host proteins independent of the canonical E1/E2/E3 pathway, they have also been shown to produce phosphoribosylated free ubiquitin. This modified ubiquitin product is incompatible with conventional E1/E2/E3 ubiquitination processes, with the potential to lock down various cellular functions that are dependent on ubiquitin signaling. Here, we show that in addition to free ubiquitin, Lys63-, Lys48-, Lys11-, and Met1-linked diubiquitin chains are also modified by SdeA in a similar fashion. Both the proximal and distal ubiquitin moieties are targeted in the phosphoribosylation reaction. Furthermore, this renders the ubiquitin chains unable to be processed by a variety of deubiquitinating enzymes. These observations broaden the scope of SdeA's modulatory functions during Legionella infection.
嗜肺军团菌效应蛋白SidE家族是一类独特的泛素修饰酶。除了催化某些宿主蛋白的NAD依赖性泛素化反应（不依赖于经典的E1/E2/E3途径）外，它们还被证明能产生磷酸核糖基化的游离泛素。这种修饰后的泛素产物与传统的E1/E2/E3泛素化过程不兼容，有可能锁定各种依赖泛素信号传导的细胞功能。在这里，我们表明，除了游离泛素外，SdeA还以类似的方式修饰了赖氨酸63、赖氨酸48、赖氨酸11和蛋氨酸1连接的双泛素链。在磷酸核糖基化反应中，近端和远端泛素部分均被靶向修饰。此外，这使得泛素链无法被多种去泛素化酶加工处理。这些观察结果拓宽了SdeA在军团菌感染过程中调节功能的范围。
