Allosteric activation of DegS, a stress sensor PDZ protease
Allosteric activation of DegS, a stress sensor PDZ protease
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DOI：
10.1016/j.cell.2007.08.044
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发表时间：
2007-11-02
期刊：
影响因子：
64.5
通讯作者：
Sauer, Robert T.
中科院分区：
文献类型：
--
作者：
Sohn, Jungsan;Grant, Robert A.;Sauer, Robert T.
调节膜内蛋白水解是细胞间信号转导的一种方法。当蛋白质折叠在大肠杆菌的外质中受损时，外膜蛋白（OMPs）的C端结合到三聚体DegS蛋白酶的PDZ结构域并激活RseA的切割，RseA是一种跨膜转录调节剂。我们在这里展示了DegS是一种变构酶。OMP结合将平衡从活性位点无反应的非功能状态转变为功能蛋白水解构象。晶体学、生化和诱变实验表明，未配体的PDZ结构域具有抑制作用，并表明OMP结合本身足以稳定松弛构象并激活DegS。omp诱导的激活和RseA结合都是积极合作的，允许OMP-DegS-RseA系统具有类似开关的行为。参与DegS变构开关的残基在DegP/HtrA和HtrA2/Omi家族中是保守的，这表明许多PDZ蛋白酶使用一个共同的变构激活机制。
Regulated intramembrane proteolysis is a method for transducing signals between cellular compartments. When protein folding is compromised in the periplasm of E. coli, the C termini of outer-membrane proteins (OMPs) bind to the PDZ domains of the trimeric DegS protease and activate cleavage of RseA, a transmembrane transcriptional regulator. We show here that DegS is an allosteric enzyme. OMP binding shifts the equilibrium from a nonfunctional state, in which the active sites are unreactive, to the functional proteolytic conformation. Crystallographic, biochemical, and mutagenic experiments show that the unliganded PDZ domains are inhibitory and suggest that OMP binding per se is sufficient to stabilize the relaxed conformation and activate DegS. OMP-induced activation and RseA binding are both positively cooperative, allowing switch-like behavior of the OMP-DegS-RseA system. Residues involved in the DegS allosteric switch are conserved in the DegP/HtrA and HtrA2/Omi families, suggesting that many PDZ proteases use a common mechanism of allosteric activation.