bims-cytox1 2024-01-14 papers

Issue of 2024‒01‒14
three papers selected by
Gavin McStay, Liverpool John Moores University

Int J Mol Sci. 2023 Dec 20. pii: 93. [Epub ahead of print]25(1):

Mitochondrial Protein SLIRP Affects Biosynthesis of Cytochrome c Oxidase Subunits in HEK293T Cells.

Mariia V Baleva, Uliana Piunova, Ivan Chicherin, Ruslan Vasilev, Sergey Levitskii, Piotr Kamenski.

Mitochondria carry out various vital roles in eukaryotic cells, including ATP energy synthesis, the regulation of apoptosis, Fe-S cluster formation, and the metabolism of fatty acids, amino acids, and nucleotides. Throughout evolution, mitochondria lost most of their ancestor's genome but kept the replication, transcription, and translation machinery. Protein biosynthesis in mitochondria is specialized in the production of highly hydrophobic proteins encoded by mitochondria. These proteins are components of oxidative phosphorylation chain complexes. The coordination of protein synthesis must be precise to ensure the correct assembly of nuclear-encoded subunits for these complexes. However, the regulatory mechanisms of mitochondrial translation in human cells are not yet fully understood. In this study, we examined the contribution of the SLIRP protein in regulating protein biosynthesis in mitochondria. Using a click-chemistry approach, we discovered that deletion of the SLIRP gene disturbs mitochondrial translation, leading to the dysfunction of complexes I and IV, but it has no significant effect on complexes III and V. We have shown that this protein interacts only with the small subunit of the mitochondrial ribosome, which may indicate its involvement in the regulation of the mitochondrial translation initiation stage.

Keywords: mitochondria; translation; translation regulation

DOI: https://doi.org/10.3390/ijms25010093

Front Chem. 2023 ;11 1186022

Reaction pathways, proton transfer, and proton pumping in ba3 class cytochrome c oxidase: perspectives from DFT quantum chemistry and molecular dynamics.

Louis Noodleman, Andreas W Götz, Wen-Ge Han Du, Laura Hunsicker-Wang.

After drawing comparisons between the reaction pathways of cytochrome c oxidase (CcO, Complex 4) and the preceding complex cytochrome bc1 (Complex 3), both being proton pumping complexes along the electron transport chain, we provide an analysis of the reaction pathways in bacterial ba3 class CcO, comparing spectroscopic results and kinetics observations with results from DFT calculations. For an important arc of the catalytic cycle in CcO, we can trace the energy pathways for the chemical protons and show how these pathways drive proton pumping of the vectorial protons. We then explore the proton loading network above the Fe heme a3-CuB catalytic center, showing how protons are loaded in and then released by combining DFT-based reaction energies with molecular dynamics simulations over states of that cycle. We also propose some additional reaction pathways for the chemical and vector protons based on our recent work with spectroscopic support.

Keywords: DFT calculations; MD simulations; bioenergetics; cytochrome c oxidase; electron transport chain; proton pumping; proton transfer; reaction pathway

DOI: https://doi.org/10.3389/fchem.2023.1186022

J Biol Chem. 2024 Jan 08. pii: S0021-9258(24)00002-4. [Epub ahead of print] 105626

Accessory subunit NDUFB4 participates in mitochondrial complex I supercomplex formation.

Gaganvir Parmar, Claire Fong-McMaster, Chantal Pileggi, David A Patten, Alexanne Cuillerier, Stephanie Myers, Ying Wang, Siegfried Hekimi, Miroslava Cuperlovic-Culf, Mary-Ellen Harper.

Mitochondrial electron transport chain (ETC) complexes organize into supramolecular structures called respiratory supercomplexes (SCs). The role of respiratory SC remains largely unconfirmed despite evidence supporting their necessity for mitochondrial respiratory function. The mechanisms underlying the formation of the I1III2IV1 "respirasome" SC are also not fully understood, further limiting insights into these processes in physiology and diseases, including neurodegeneration and metabolic syndromes. NDUFB4 is a complex I accessory subunit that contains residues that interact with the subunit UQCRC1 from complex III, suggesting that NDUFB4 is integral for I1III2IV1 respirasome integrity. Here, we introduced specific point mutations to Asn24 (N24) and Arg30 (R30) residues on NDUFB4 to decipher the role of I1III2-containing respiratory SCs in cellular metabolism while minimizing the functional consequences to complex I assembly. Our results demonstrate that NDUFB4 point mutations N24A and R30A impair I1III2IV1 respirasome assembly and reduce mitochondrial respiratory flux. Steady-state metabolomics also revealed a global decrease in TCA cycle metabolites, affecting NADH-generating substrates. Taken together, our findings highlight an integral role of NDUFB4 in respirasome assembly and demonstrate the functional significance of SCs in regulating mammalian cell bioenergetics.

Keywords: Mitochondria; NDUFB4; electron transport chain; oxidative phosphorylation; respirasome; steady-state metabolomics; supercomplexes

DOI: https://doi.org/10.1016/j.jbc.2024.105626