In eukaryotic cells, mitochondria perform cellular respiration through a series of redox reactions ultimately reducing molecular oxygen to water. The system responsible for this process is the respiratory chain or electron transport system (ETS) composed of complexes I–IV. Due to its function, the ETS is the main source of reactive oxygen species (ROS), generating them on both sides of the mitochondrial inner membrane, i.e. the intermembrane space (IMS) and the matrix. A correct balance between ROS generation and scavenging is important for keeping the cellular redox homeostasis and other important aspects of cellular physiology. However, ROS generated in the mitochondria are important signaling molecules regulating mitochondrial biogenesis and function. The IMS contains a large number of redox sensing proteins, containing specific Cys-rich domains, that are involved in ETS complex biogenesis. The large majority of these proteins function as cytochrome c oxidase (COX) assembly factors, mainly for the handling of copper ions necessary for the formation of the redox reactive catalytic centers. A particular case of ROS-regulated COX assembly factor is COA8, whose intramitochondrial levels are increased by oxidative stress, promoting COX assembly and/or protecting the enzyme from oxidative damage. In this review, we will discuss the current knowledge concerning the role played by ROS in regulating mitochondrial activity and biogenesis, focusing on the COX enzyme and with a special emphasis on the functional role exerted by the redox sensitive Cys residues contained in the COX assembly factors.
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Cover Image
Cover Image
Single-molecule imaging techniques have revealed the dynamic nature of ion channels and shown that channel activity is sometimes dependent on their mobility and mechanical forces in the lipid membrane. The cover image shows a recent high-resolution cryo-EM image of the two-pore structure of the core complex of the mitochondrial outer membrane protein translocase (TOM) from the filamentous fungus
Neurospora crassa , together with a single-molecule false-color image illustrating the calcium flux through its two pores associated with conformational changes of this protein complex. The TOM core complex undergoes reversible transitions between active (high intensity pink dots), weakly active (medium intensity pink dots) and inactive (low intensity pink dots) channel states corresponding to the suspension of movement. For more information, see the article by Nussberger and colleagues (pp. 911–922) in this issue. Image provided by Shuo Wang.
Emerging mechanisms in the redox regulation of mitochondrial cytochrome c oxidase assembly and function
Suleva Povea-Cabello, Michele Brischigliaro, Erika Fernández-Vizarra; Emerging mechanisms in the redox regulation of mitochondrial cytochrome c oxidase assembly and function. Biochem Soc Trans 24 April 2024; 52 (2): 873–885. doi: https://doi.org/10.1042/BST20231183
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