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POLRMT is the dedicated mitochondrial RNA polymerase in metazoans and is essential for priming mitochondrial DNA (mtDNA) synthesis. Aberrant POLRMT causes mitochondrial dysfunction and has previously been linked to human metabolic disease. The small molecule IMT1B is an allosteric inhibitor of POLRMT, and its use in diverse model organisms is informative about various aspects of mtDNA synthesis and transcription. Previously, this drug has been shown to be effective in perturbing mtDNA gene expression in human cells and mice. Moreover, a leucine to phenylalanine substitution at position 813 of human POLRMT is predicted to disrupt interaction with the drug. However, the effect of the F813L mutation on the efficacy of POLRMT inhibition (POLRMTi) has not been rigorously tested. Here, we determined by multiple sequence alignment and phylogenetic analysis that this mutation in POLRMT is common among invertebrates, including the model nematode Caenorhabditis elegans. AlphaFold analyses of metazoan POLRMT folding suggest that the F813L substitution alters the physicochemical features of the IMT1B binding pocket. Finally, we find that IMT1B treatment of larval Caenorhabditis elegans has little impact on mtDNA copy number, suggesting that POLRMTi via IMT1B may not be effective in this model organism.
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Coenzyme Q10 trapping in mitochondrial complex I underlies Leber’s hereditary optic neuropathy
How does a single amino acid mutation occurring in the blinding disease, Leber’s hereditary optic neuropathy (LHON), impair electron shuttling in mitochondria? We investigated changes induced by the m.3460 G>A mutation in mitochondrial protein ND1 using the tools of Molecular Dynamics and Free Energy Perturbation simulations, with the goal of determining the mechanism by which this mutation affects mitochondrial function. A recent analysis suggested that the mutation’s replacement of alanine A52 with a threonine perturbs the stability of a region where binding of the electron shuttling protein, Coenzyme Q10, occurs. We found two functionally opposing changes involving the role of Coenzyme Q10. The first showed that quantum electron transfer from the terminal Fe/S complex, N2, to the Coenzyme Q10 headgroup, docked in its binding pocket, is enhanced. However, this positive adjustment is overshadowed by our finding that the mobility of Coenzyme Q10 in its oxidized and reduced states, entering and exiting its binding pocket, is disrupted by the mutation in a manner that leads to conditions promoting the generation of reactive oxygen species. An increase in reactive oxygen species caused by the LHON mutation has been proposed to be responsible for this optic neuropathy.
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- Award ID(s):
- 2203366
- PAR ID:
- 10523093
- Publisher / Repository:
- NAS
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 120
- Issue:
- 39
- ISSN:
- 0027-8424
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1073/pnas.2304884120
