bims-tricox 2026-07-26 papers

Issue of 2026–07–26
two papers selected by
Yash Verma, Universität Zürich

Biochim Biophys Acta Mol Cell Res. 2026 Jul 20. pii: S0167-4889(26)00093-5. [Epub ahead of print]1873(7): 120194

Orchestration of OXPHOS biogenesis through regulation of mitochondrial translation.

Andreas Carlström, Carmela Vazquez-Calvo, Martin Ott.

Mitochondrial gene expression is a remnant of the endosymbiotic origin of the organelle, which contains a complete gene expression system that contributes only a handful of subunits to the complexes driving oxidative phosphorylation (OXPHOS). During evolution, many processes of gene expression in mitochondria have diverged from the bacterial ancestor. A central problem to assemble oxidative phosphorylation complexes is that they contain subunits from two genetic sources. Hence, mechanisms have evolved to synchronize expression of nuclear and mitochondrial genes to avoid problems with stoichiometry, which could hamper their assembly. Here, we will summarize recent insights into how gene expression operates with a focus on the mechanisms related to the control of mitochondrial translation in yeast and human cells.

Keywords: Evolution; Gene expression; Mitochondria; Mitoribosomes; Translation initiation; Translational activators; Translational regulation

DOI: https://doi.org/10.1016/j.bbamcr.2026.120194

Nat Struct Mol Biol. 2026 Jul 23.

Direct coupling of human TOM and TIM22 complexes drives mitochondrial carrier import.

Xiaolong Liu, Hongjun Cai, Hao Wang, Xueyin Zhou, Yutong Zhang, Shuai Liu, Jiajun Zhu, Long Li.

Metabolite carriers that control essential metabolite transport are imported into mitochondria through the TOM and TIM22 complexes. How TOM and TIM22 coordinate in human mitochondria has remained largely unknown. Here we show that human TOM and TIM22 assemble into a supercomplex that seamlessly couples carrier translocation across the outer and inner membranes, unlike in yeast where the two complexes appear to function separately. Cryo-electron microscopy structures of the human TOM-TIM22 supercomplex reveal unpaired carrier transmembrane segments traversing the TOM channel along a hydrophobic path and exiting through an unexpected lateral groove outside the channel. The membrane-bound small Tim subunits provide the substrate entry site for TIM22, while a membrane-exposed groove of TIM22 serves as the exit for carrier insertion into the inner membrane. These findings provide insights into the human carrier translocation pathway at molecular resolution and establish the TOM-TIM22 supercomplex as a central organizing unit of mitochondrial carrier import.

DOI: https://doi.org/10.1038/s41594-026-01849-w