Molecular Adaptation of the DegQ Protease to Exert Protein Quality Control in the Bacterial Cell Envelope
Molecular Adaptation of the DegQ Protease to Exert Protein Quality Control in the Bacterial Cell Envelope
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DOI：
10.1074/jbc.m111.243832
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发表时间：
2011-09-02
影响因子：
4.8
通讯作者：
Clausen, Tim
中科院分区：
文献类型：
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作者：
Sawa, Justyna;Malet, Helene;Clausen, Tim
为了对不同的应激情况做出反应并防止错误折叠蛋白质的积累，所有细胞都使用多种蛋白酶和伴侣蛋白，它们共同建立了一个有效的蛋白质质量控制系统。大肠杆菌细胞包膜中蛋白质的功能性由HtrA蛋白酶DegS、DegP和DegQ监测。与DegP和DegS相比，DegQ的结构和功能尚未详细说明。在这里，我们表明，底物结合触发转换的休息DegQ六聚体转化为催化活性的12-和24-聚体。有趣的是，底物诱导的寡聚体重组和蛋白酶激活依赖于第一个PDZ结构域，但不依赖于第二个。因此，最初在DegP中鉴定的调节机制应该是HtrA蛋白酶的共同特征，其中大多数蛋白酶仅包含单个PDZ结构域。使用缺乏第二PDZ结构域的DegQ突变体，我们确定了十二聚体HtrA复合物的高分辨率晶体结构。12和24梅里克HtrA复合物中蛋白酶和PDZ结构域几乎相同的结构域取向揭示了保守的PDZ 1-> L3 -> LD/L1/L2信号级联，其中L3环感知更高级的底物结合颗粒的重新定位的PDZ 1结构域并激活蛋白酶功能。此外，我们的体外和体内数据暗示DegQ在细菌细胞包膜中的pH相关功能。
To react to distinct stress situations and to prevent the accumulation of misfolded proteins, all cells employ a number of proteases and chaperones, which together set up an efficient protein quality control system. The functionality of proteins in the cell envelope of Escherichia coli is monitored by the HtrA proteases DegS, DegP, and DegQ. In contrast with DegP and DegS, the structure and function of DegQ has not been addressed in detail. Here, we show that substrate binding triggers the conversion of the resting DegQ hexamer into catalytically active 12- and 24-mers. Interestingly, substrate-induced oligomer reassembly and protease activation depends on the first PDZ domain but not on the second. Therefore, the regulatory mechanism originally identified in DegP should be a common feature of HtrA proteases, most of which encompass only a single PDZ domain. Using a DegQ mutant lacking the second PDZ domain, we determined the high resolution crystal structure of a dodecameric HtrA complex. The nearly identical domain orientation of protease and PDZ domains within 12and 24-meric HtrA complexes reveals a conserved PDZ1 -> L3 -> LD/L1/L2 signaling cascade, in which loop L3 senses the repositioned PDZ1 domain of higher order, substrate-engaged particles and activates protease function. Furthermore, our in vitro and in vivo data imply a pH-related function of DegQ in the bacterial cell envelope.