Structural Analysis of the Bacterial Effector AvrA Identifies a Critical Helix Involved in Substrate Recognition
Structural Analysis of the Bacterial Effector AvrA Identifies a Critical Helix Involved in Substrate Recognition
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DOI：
10.1021/acs.biochem.8b00512
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发表时间：
2018-08-21
期刊：
影响因子：
2.9
通讯作者：
Nagar, Bhushan
中科院分区：
文献类型：
--
作者：
Labriola, Jonathan M.;Zhou, Yifan;Nagar, Bhushan
细菌效应蛋白通过操纵宿主免疫反应途径，对病原菌的感染和增殖起着至关重要的作用。Avra是一种沙门氏菌效应因子，属于YopJ乙酰基转移酶家族，它通过丝裂原激活的受体激酶4和7(MKK4/7)的乙酰化来抑制哺乳动物中的c-jun氨基末端激酶(JNK)信号。有趣的是，Avra有两个类似物，它们只有一个内部亮氨酸残基不同，当没有这个残基时(Avra(Delta L140))就失去了抑制JNK信号的能力。在这里，我们提出了第一个来自动物病原体Avra(Delta L140)的细菌效应器的晶体结构，并伴随着两个Avra变体的全面生物物理特征。在六磷酸肌醇和辅酶A的复合体中，结构显示了两个密切相关的结构域，由一个类似CE家族多肽酶的催化核心和一个楔形的调节区组成，后者介导辅因子和底物的结合。Avra(Delta L140)功能的丧失是由于它不能与MKK4/7相互作用，而MKK4/7最终是由于与含有L140的活性部位相邻的关键螺旋的构象改变而引起的。这些结果提供了对YopJ乙酰基转移酶家族底物识别的一般见解。
Bacterial effector proteins are essential for the infection and proliferation of pathogenic bacteria through manipulation of host immune response pathways. AvrA is a Salmonella effector that belongs to the YopJ family of acetyltransferases, which suppresses c-JUN N-terminal kinase (JNK) signaling in mammals through acetylation of mitogen-activated receptor kinase kinases 4 and 7 (MKK4/7). Interestingly, there are two paralogues of AvrA that differ by only a single internal leucine residue, which when absent (AvrA(Delta L140)) abrogates the ability to suppress JNK signaling. Here, we present the first crystal structure of a bacterial effector from an animal pathogen, AvrA(Delta L140), accompanied by a thorough biophysical characterization of both AvrA variants. The structure in complex with inositol hexaphosphate and coenzyme A reveals two closely associated domains consisting of a catalytic core that resembles the CE clan peptidases and a wedge-shaped regulatory region that mediates cofactor and substrate binding. The loss of the putative function of AvrA(Delta L140 )is due to its inability to interact with MKK4/7, which ultimately arises from an altered conformation of a critical helix adjacent to the active site that harbors L140. These results provide general insights into substrate recognition across the YopJ family of acetyltransferases.