bims-mitran 2026-08-30 papers

Issue of 2026–08–30
two papers selected by
Andreas Kohler, Umeå University

Sci Adv. 2026 Aug 28. 12(35): eaeg8792

Loss of the mitochondrial SAM transporter reveals a lipoylation-dependent metabolic vulnerability in the postnatal heart.

The neonatal heart experiences rapid metabolic growth after birth to meet increasing energetic and biosynthetic demands. How mitochondrial cofactor availability limits this transition remains unclear. Here, we demonstrate that mitochondrial S-adenosylmethionine (mitoSAM) import through SLC25A26 becomes limiting shortly after birth and specifically restricts protein lipoylation, although other mitoSAM-dependent processes are partially preserved. Loss of Slc25a26 impaired lipoylation-dependent flux through pyruvate and α-ketoglutarate dehydrogenases, restricting tricarboxylic acid cycle carbon entry and depleting aspartate and nucleotide pools. Conversely, mitochondrial gene expression remained intact, and respiratory chain enzyme activities showed partial impairment, indicating that lipoylation is the most mitoSAM-sensitive pathway during postnatal heart adaptation. These metabolic limitations were linked to sustained cardiomyocyte cell-cycle activity, delayed structural maturation, and early cardiomyopathy. Supplementing with medium-chain triglycerides during the suckling-to-weaning transition partially stabilized metabolism and prolonged survival. Overall, our findings identify a stage-specific metabolic vulnerability in the postnatal heart characterized by hierarchical mitoSAM utilization within the mitochondria.

DOI: https://doi.org/10.1126/sciadv.aeg8792

J Struct Biol. 2026 Aug 27. pii: S1047-8477(26)00075-4. [Epub ahead of print] 108359

Structural basis of Saccharomyces cerevisiae Mba1 in mitochondrial co-translational membrane insertion.

Jing Yang, Maosen Ruan, Dongshuai Bai, Yong Liu, Yizhuo Wang, Hengfang Tang, Yunyan Li, Junfeng Wang.

Co-translational membrane insertion is essential for the efficient integration of mitochondrially encoded proteins into the inner mitochondrial membrane (IMM) and is critical for respiratory chain biogenesis. Mba1 is a mitochondrial ribosome-associated protein implicated in coupling mitochondrial translation with inner-membrane protein biogenesis, but its structural basis of function remains poorly understood. Here, we determined the solution structure of mature Saccharomyces cerevisiae Mba1 (mMba1) using multidimensional nuclear magnetic resonance (NMR) spectroscopy. The structure reveals a compact α + β fold with a central hydrophobic cavity and distinct charged surface regions. Ribosome titration, paramagnetic relaxation enhancement, and Cox2-derived peptide titration identified several regions of mMba1 that are affected by these different interaction conditions. Mapping these regions onto the structure reveals spatially distinct surfaces that may contribute to ribosome association, membrane proximity, and interactions with hydrophobic peptide segments. These findings provide a structural framework for interpreting previous functional studies of Mba1 and support a working model in which Mba1 may function as a peripheral adaptor at the mitoribosome-inner membrane interface. Further structural and biochemical studies will be required to establish the molecular mechanisms underlying these interactions.

Keywords: Co-translational insertion; Mba1; Membrane association; NMR; Ribosome

DOI: https://doi.org/10.1016/j.jsb.2026.108359