The mitochondrial serine protease HtrA2 is a human homolog of the Escherichia coli Deg-proteins exhibiting chaperone and proteolytic roles. HtrA2 is involved in both apoptotic regulation via its ability to degrade inhibitor-of-apoptosis proteins (IAPs), as well as in cellular maintenance as part of the cellular protein quality control machinery, by preventing the possible toxic accumulation of aggregated proteins. In this study, we use advanced solution NMR spectroscopy methods combined with biophysical characterization and biochemical assays to elucidate the crucial role of the substrate recognizing PDZ domain. This domain regulates the protease activity of HtrA2 by triggering an intricate allosteric network involving the regulatory loops of the protease domain. We further show that divalent metal ions can both positively and negatively modulate the activity of HtrA2, leading to a refined model of HtrA2 regulation within the apoptotic pathway.

线粒体丝氨酸蛋白酶 HtrA2 是大肠杆菌 Deg 蛋白的人同源物，具有伴侣和蛋白水解作用。HtrA2 通过其降解凋亡抑制剂蛋白 （IAP） 的能力参与凋亡调节，以及作为细胞蛋白质质量控制机制的一部分，通过防止聚集蛋白可能的毒性积累来参与细胞维持。在这项研究中，我们使用先进的溶液 NMR 波谱方法结合生物物理表征和生化分析来阐明底物识别 PDZ 结构域的关键作用。该结构域通过触发涉及蛋白酶结构域调节环的复杂变构网络来调节 HtrA2 的蛋白酶活性。我们进一步表明，二价金属离子可以正向和负向调节 HtrA2 的活性，从而在凋亡途径内形成 HtrA2 调节的精细模型。