一个E1-E2融合蛋白在细菌中启动抗病毒免疫信号
Hannah E Ledvina1, Qiaozhen Ye2, Yajie Gu2
1Department of Biochemistry, University of Colorado Boulder, Boulder, CO, USA.
Nature
|February 9, 2023
概括
细菌使用类似于Ubiquitin转移酶的系统,涉及Cap2和Cap3蛋白质来控制对细菌感染的先天免疫信号. 这种古老的机制启动循环GMP-AMP合成酶 (cGAS) 类核基转移酶 (CD-NTases) 的激活.
科学领域:
- 微生物学
- 免疫学
- 分子生物学
背景情况:
- 天生的免疫依赖于感知感染并激活反应,同时防止自身免疫.
- 人类循环GMP- AMP合成酶 (cGAS) 检测病毒感染,通过STING产生循环GMP- AMP (cGAMP) 进行抗病毒信号.
- 细菌拥有CD-NTase,这是cGAS的进化前体,可以检测菌体并产生核酸第二信使.
研究的目的:
- 阐明控制细菌CD-NTase激活的机制.
- 研究CD-NTase相关蛋白2 (Cap2) 在细菌免疫信号传递中的作用.
- 了解类似于ubiquitin转移酶的机器的进化起源.
主要方法:
- 用冷电子显微镜来确定Cap2-CD-NTase复合物的结构.
- 生物化学测试以表征Cap2的泛素转移酶类活性.
- 酶试验以研究内酶Cap3的功能.
主要成果:
- Cap2 作为一种全在一体的泛素转移酶,启动 CD- NTases 进行激活.
- 一个反应性中间状态显示Cap2将CD-NTase C终端与AMP结合起来.
- Cap2的活性由一个能切割CD-NTase基的内酶Cap3平衡.
- 这种系统可增强循环GMP-AMP (cGAMP) 的产生.
结论:
- 细菌利用一种简化,古老的泛素转移酶类系统来控制免疫信号.
- 这种机制提供了对E1和E2无处不在酶在生命领域的演变的洞察.
- Cap2-Cap3系统代表了调节细菌内在免疫反应的保存策略.
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