Departamento de Bioquímica, Facultad de Medicina, Universidad de La República, Montevideo, Uruguay; Centro de Investigaciones Biomédicas (CEINBIO), Universidad de la República, Montevideo, Uruguay.
Centro de Investigaciones Biomédicas (CEINBIO), Universidad de la República, Montevideo, Uruguay.
Arch Biochem Biophys. 2021 May 30;703:108824. doi: 10.1016/j.abb.2021.108824. Epub 2021 Mar 4.
The interaction between cytochrome c and cardiolipin is a relevant process in the mitochondrial redox homeostasis, playing roles in the mechanism of electron transfer to cytochrome c oxidase and also modulating cytochrome c conformation, reactivity and function. Peroxynitrite is a widespread nitrating agent formed in mitochondria under oxidative stress conditions, and can result in the formation of tyrosine nitrated cytochrome c. Some of the nitro-cytochrome c species undergo conformational changes at physiological pH and increase its peroxidase activity. In this work we evaluated the influence of cardiolipin on peroxynitrite-mediated cytochrome c nitration yields and site-specificity. Our results show that cardiolipin enhances cytochrome c nitration by peroxynitrite and targets it to heme-adjacent Tyr67. Cytochrome c nitration also modifies the affinity of protein with cardiolipin. Using a combination of experimental techniques and computer modeling, it is concluded that structural modifications in the Tyr67 region are responsible for the observed changes in protein-derived radical and tyrosine nitration levels, distribution of nitrated proteoforms and affinity to cardiolipin. Increased nitration of cytochrome c in presence of cardiolipin within mitochondria and the gain of peroxidatic activity could then impact events such as the onset of apoptosis and other processes related to the disruption of mitochondrial redox homeostasis.
细胞色素 c 与心磷脂的相互作用是线粒体氧化还原动态平衡中的一个相关过程，在电子向细胞色素 c 氧化酶转移的机制中发挥作用，同时调节细胞色素 c 的构象、反应性和功能。过氧亚硝酸盐是一种广泛存在的硝化剂，在氧化应激条件下形成于线粒体中，可导致酪氨酸硝化细胞色素 c 的形成。一些硝基细胞色素 c 物种在生理 pH 值下发生构象变化，增加其过氧化物酶活性。在这项工作中，我们评估了心磷脂对过氧亚硝酸盐介导的细胞色素 c 硝化产率和特异性的影响。我们的结果表明，心磷脂增强了过氧亚硝酸盐介导的细胞色素 c 硝化作用，并将其靶向血红素附近的 Tyr67。细胞色素 c 的硝化也改变了蛋白与心磷脂的亲和力。通过实验技术和计算机建模的结合，我们得出结论，Tyr67 区域的结构修饰是导致观察到的蛋白衍生自由基和酪氨酸硝化水平、硝化蛋白形式的分布以及与心磷脂亲和力变化的原因。在线粒体中存在心磷脂的情况下，细胞色素 c 的硝化增加和过氧化物酶活性的增加可能会影响细胞凋亡的发生和其他与线粒体氧化还原动态平衡破坏相关的过程。
