Bioinformatics Institute, Agency for Science, Technology and Research (A*STAR), 30 Biopolis Street, #07-01 Matrix, Singapore, 138671, Republic of Singapore.
School of Computer Engineering, Nanyang Technological University (NTU), 50 Nanyang Drive, Singapore, 637553, Republic of Singapore.
Sci Rep. 2018 Sep 20;8(1):14151. doi: 10.1038/s41598-018-32527-7.
Peroxiredoxins (Prxs) are ubiquitous antioxidants utilizing a reactive cysteine for peroxide reduction and acting as a molecular chaperone under various stress conditions. Besides other stimulating factors, oxidative- and heat stress conditions trigger their ATP-independent chaperoning function. So far, many studies were intended to reveal the chaperoning mechanisms of the so-called sensitive Prxs of eukaryotes, which are susceptible to inactivation by over-oxidation of its reactive cysteine during HO reduction. In contrast, the chaperone mechanisms of bacterial Prxs, which are mostly robust against inactivation by over-oxidation, are not well understood. Herein, comprehensive biochemical and biophysical studies demonstrate that the Escherichia coli alkyl hydroperoxide reductase subunit C (EcAhpC) acquires chaperone activity under heat stress. Interestingly, their chaperoning activity is independent of its redox-states but is regulated in a temperature-dependent manner. Data are presented, showing that oxidized EcAhpC, which forms dimers at 25 °C, self-assembled into high molecular weight (HMW) oligomers at higher temperatures and supressed aggregation of client proteins at heat-shock conditions. In addition, we unravelled the essential role of the C-terminal tail of EcAhpC on heat-induced HMW oligomer formation and chaperoning activity. Our findings suggest a novel molecular mechanism for bacterial Prxs to function as chaperone at heat-shock conditions.
过氧化物酶（Prxs）是一种普遍存在的抗氧化剂，利用一个反应性半胱氨酸来还原过氧化物，并在各种应激条件下充当分子伴侣。除了其他刺激因素外，氧化和热应激条件会触发其 ATP 非依赖性伴侣功能。到目前为止，许多研究旨在揭示所谓的真核生物敏感 Prxs 的伴侣机制，这些 Prxs 的活性半胱氨酸在 HO 还原过程中容易因过度氧化而失活。相比之下，细菌 Prxs 的伴侣机制不太清楚，这些 Prxs 大多不易因过度氧化而失活。在此，全面的生化和生物物理研究表明，大肠杆菌烷基氢过氧化物还原酶亚基 C（EcAhpC）在热应激下获得伴侣活性。有趣的是，它们的伴侣活性不依赖于其氧化还原状态，而是以温度依赖的方式调节。有数据表明，在 25°C 下形成二聚体的氧化 EcAhpC 在较高温度下自组装成高分子量（HMW）寡聚物，并在热休克条件下抑制了客户蛋白的聚集。此外，我们揭示了 EcAhpC C 末端尾巴在热诱导的 HMW 寡聚物形成和伴侣活性中的重要作用。我们的研究结果表明，细菌 Prxs 在热休克条件下作为伴侣发挥作用的一种新的分子机制。
