The Helicobacter pylori HtrA protein (HtrA_Hp) is an important virulence factor involved in the infection process by proteolysis of components of the tight (claudin‐8 and occludin) and adherens junctions (E‐cadherin) between epithelial cells. As a protease and chaperone, HtrA_Hp is involved in protein quality control, which is particularly important under stress conditions. HtrA_Hp contains a protease domain and two C‐terminal PDZ domains (PDZ1 and PDZ2). In the HtrA protein family, the PDZ domains are proposed to play important roles, including regulation of proteolytic activity. We therefore mutated the PDZ1 and PDZ2 domains in HtrA_Hp and studied the maintenance of proteolytic activity, assembly and rearrangement of the corresponding oligomeric forms. Our in vitro experiments demonstrated that at least PDZ1 is important for efficient substrate cleavage_, while both PDZ domains are dispensable for the chaperone‐like activity. However, in living H. pylori cells, only the mutant containing at least PDZ1, but not PDZ2, ensured bacterial growth under stressful conditions. Moreover, we can demonstrate that PDZ1 is crucial for HtrA_Hp oligomerization. Interestingly, all truncated proteolytically active HtrA_Hp variants were functional in the in vitro infection assay and caused damage to the E‐cadherin‐based adherens junctions. These findings provide valuable new insights into the function of HtrA_Hp in an important pathogen of humans.

中文翻译：

---

两个 PDZ 结构域对幽门螺杆菌丝氨酸蛋白酶 HtrA 蛋白水解和分子伴侣活性的重要性

的幽门螺杆菌的hTRA蛋白（的hTRA_的Hp）是由紧（密蛋白-8和闭合蛋白）的组分的蛋白水解中涉及的感染过程中的重要毒力因子和粘着上皮细胞间连接（E-钙粘蛋白）。作为蛋白酶和分子伴侣，HtrA _Hp参与蛋白质质量控​​制，这在压力条件下尤为重要。HtrA _Hp包含一个蛋白酶结构域和两个 C 端 PDZ 结构域（PDZ1 和 PDZ2）。在 HtrA 蛋白家族中，PDZ 域被提议发挥重要作用，包括调节蛋白水解活性。因此，我们突变了 HtrA _{Hp 中}的 PDZ1 和 PDZ2 域并研究了蛋白水解活性的维持、相应寡聚形式的组装和重排。我们的体外实验表明，至少 PDZ1 对有效的底物切割很重要_，而两个 PDZ 结构域对于分子伴侣样活性都是可有可无的。然而，在活的幽门螺杆菌细胞中，只有至少含有 PDZ1 而不是 PDZ2 的突变体才能确保细菌在压力条件下生长。此外，我们可以证明 PDZ1 对 HtrA _Hp寡聚化至关重要。有趣的是，所有截断的蛋白水解活性 HtrA _Hp变体在体外都具有功能感染测定并对基于 E-钙粘蛋白的粘附连接造成损害。这些发现为 HtrA _Hp在人类重要病原体中的功能提供了宝贵的新见解。