Bioinformatics Institute, Agency for Science, Technology and Research (A⁎STAR), 30 Biopolis Street, #07-01 Matrix, Singapore 138671, Republic of Singapore.
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.
Free Radic Biol Med. 2018 Apr;118:59-70. doi: 10.1016/j.freeradbiomed.2018.02.027. Epub 2018 Feb 21.
Peroxiredoxins (Prxs) catalyse the rapid reduction of hydrogen peroxide, organic hydroperoxide and peroxynitrite, using a fully conserved peroxidatic cysteine (C) located in a conserved sequence Pxxx(T/S)xxC motif known as C-loop. In addition, Prxs are involved in cellular signaling pathways and regulate several redox-dependent process related disease. The effective catalysis of Prxs is associated with alterations in the C-loop between reduced, Fully Folded (FF), and oxidized, Locally Unfolded (LU) conformations, which are linked to dramatic changes in the oligomeric structure. Despite many studies, little is known about the precise structural and dynamic roles of the C-loop on Prxs functions. Herein, the comprehensive biochemical and biophysical studies on Escherichia coli alkyl hydroperoxide reductase subunit C (EcAhpC) and the C-loop mutants, EcAhpC-F45A and EcAhpC-F45P reveal that the reduced form of the C-loop adopts conformational dynamics, which is essential for effective peroxide reduction. Furthermore, the point mutants alter the structure and dynamics of the reduced form of the C-loop and, thereby, affect substrate binding, catalysis, oligomerization, stability and overoxidiation. In the oxidized form, due to restricted C-loop dynamics, the EcAhpC-F45P mutant favours a decamer formation, which enhances the effective recycling by physiological reductases compared to wild-type EcAhpC. In addition, the study reveals that residue F45 increases the specificity of Prxs-reductase interactions. Based on these studies, we propose an evolution of the C-loop with confined sequence conservation within Prxs subfamilies that might optimize the functional adaptation of Prxs into various physiological roles.
过氧化物酶（Prxs）利用完全保守的过氧催化半胱氨酸（C）在保守序列 Pxxx（T/S）xxC 基序（称为 C 环）中快速还原过氧化氢、有机过氧化物和过氧亚硝酸盐。此外，Prxs 参与细胞信号通路并调节几种与氧化还原相关的疾病过程。Prxs 的有效催化与还原、完全折叠（FF）和氧化、局部展开（LU）构象之间的 C 环变化有关，这与寡聚结构的剧烈变化有关。尽管进行了许多研究，但对于 C 环在 Prxs 功能中的精确结构和动态作用知之甚少。在此，对大肠杆菌烷烃氢过氧化物还原酶亚基 C（EcAhpC）和 C 环突变体 EcAhpC-F45A 和 EcAhpC-F45P 的全面生化和生物物理研究表明，C 环的还原形式采用构象动力学，这对于有效过氧化物还原至关重要。此外，点突变改变了 C 环还原形式的结构和动力学，从而影响底物结合、催化、寡聚化、稳定性和过氧氧化。在氧化形式下，由于 C 环动力学受限，EcAhpC-F45P 突变体有利于形成十聚体，与野生型 EcAhpC 相比，这增强了生理还原剂的有效循环。此外，该研究表明残基 F45 增加了 Prxs-还原酶相互作用的特异性。基于这些研究，我们提出了 C 环的进化，在 Prxs 亚家族内具有受限的序列保守性，这可能优化了 Prxs 适应各种生理作用的功能。
