Atp23p and Atp10p coordinate to regulate the assembly of yeast mitochondrial ATP synthase

The biogenesis and regulation of the plant oxidative phosphorylation system

Mitochondria are central organelles for respiration in plants. At the heart of this process is oxidative phosphorylation (OXPHOS) system, which generates ATP required for cellular energetic needs. OXPHOS complexes comprise of multiple subunits that originated from both mitochondrial and nuclear genome, which requires careful orchestration of expression, translation, import, and assembly. Constant exposure to reactive oxygen species due to redox activity also renders OXPHOS subunits to be more prone to oxidative damage, which requires coordination of disassembly and degradation. In this review, we highlight the composition, assembly, and activity of OXPHOS complexes in plants based on recent biochemical and structural studies. We also discuss how plants regulate the biogenesis and turnover of OXPHOS subunits and the importance of OXPHOS in overall plant respiration. Further studies in determining the regulation of biogenesis and activity of OXPHOS will advances the field, especially in understanding plant respiration and its role to plant growth and development.

Kub3 Deficiency Causes Aberrant Late Embryonic Lung Development in Mice by the FGF Signaling Pathway

As a Ku70-binding protein of the KUB family, Kub3 has previously been reported to play a role in DNA double-strand break repair in human glioblastoma cells in glioblastoma patients. However, the physiological roles of Kub3 in normal mammalian cells remain unknown. In the present study, we generated Kub3 gene knockout mice and revealed that knockout (KO) mice died as embryos after E18.5 or as newborns immediately after birth. Compared with the lungs of wild-type (WT) mice, Kub3 KO lungs displayed abnormal lung morphogenesis and pulmonary atelectasis at E18.5. No difference in cell proliferation or cell apoptosis was detected between KO lungs and WT lungs. However, the differentiation of alveolar epithelial cells and the maturation of type II epithelial cells were impaired in KO lungs at E18.5. Further characterization displayed that Kub3 deficiency caused an abnormal FGF signaling pathway at E18.5. Taking all the data together, we revealed that Kub3 deletion leads to abnormal late lung development in mice, resulting from the aberrant differentiation of alveolar epithelial cells and the immaturation of type II epithelial cells due to the disturbed FGF signaling pathway. Therefore, this study has uncovered an essential role of Kub3 in the prenatal lung development of mice which advances our knowledge of regulatory factors in embryonic lung development and provides new concepts for exploring the mechanisms of disease related to perinatal lung development.

T1121G Point Mutation in the Mitochondrial Gene COX1 Suppresses a Null Mutation in ATP23 Required for the Assembly of Yeast Mitochondrial ATP Synthase

Nuclear-encoded Atp23 was previously shown to have dual functions, including processing the yeast Atp6 precursor and assisting the assembly of yeast mitochondrial ATP synthase. However, it remains unknown whether there are genes functionally complementary to ATP23 to rescue atp23 null mutant. In the present paper, we screen and characterize three revertants of atp23 null mutant and reveal a T1121G point mutation in the mitochondrial gene COX1 coding sequence, which leads to Val374Gly mutation in Cox1, the suppressor in the revertants. This was verified further by the partial restoration of mitochondrial ATP synthase assembly in atp23 null mutant transformed with exogenous hybrid COX1 T1121G mutant plasmid. The predicted tertiary structure of the Cox1 p.Val374Gly mutation showed no obvious difference from wild-type Cox1. By further chase labeling with isotope [³⁵S]-methionine, we found that the stability of Atp6 of ATP synthase increased in the revertants compared with the atp23 null mutant. Taking all the data together, we revealed that the T1121G point mutation of mitochondrial gene COX1 could partially restore the unassembly of mitochondrial ATP synthase in atp23 null mutant by increasing the stability of Atp6. Therefore, this study uncovers a gene that is partially functionally complementary to ATP23 to rescue ATP23 deficiency, broadening our understanding of the relationship between yeast the cytochrome c oxidase complex and mitochondrial ATP synthase complex.

The assembly, regulation and function of the mitochondrial respiratory chain

The mitochondrial oxidative phosphorylation system is central to cellular metabolism. It comprises five enzymatic complexes and two mobile electron carriers that work in a mitochondrial respiratory chain. By coupling the oxidation of reducing equivalents coming into mitochondria to the generation and subsequent dissipation of a proton gradient across the inner mitochondrial membrane, this electron transport chain drives the production of ATP, which is then used as a primary energy carrier in virtually all cellular processes. Minimal perturbations of the respiratory chain activity are linked to diseases; therefore, it is necessary to understand how these complexes are assembled and regulated and how they function. In this Review, we outline the latest assembly models for each individual complex, and we also highlight the recent discoveries indicating that the formation of larger assemblies, known as respiratory supercomplexes, originates from the association of the intermediates of individual complexes. We then discuss how recent cryo-electron microscopy structures have been key to answering open questions on the function of the electron transport chain in mitochondrial respiration and how supercomplexes and other factors, including metabolites, can regulate the activity of the single complexes. When relevant, we discuss how these mechanisms contribute to physiology and outline their deregulation in human diseases.