bims-cytox1 2023-04-30 papers

Issue of 2023‒04‒30
five papers selected by
Gavin McStay
Liverpool John Moores University

FEBS Lett. 2023 Apr 28.

The N-terminal region of yeast mitoribosomal Mrp7/bL27m protein serves to optimize translation of nascent chains competent for OXPHOS complex assembly.

Jessica M Anderson, Jodie M Box, Rosemary A Stuart.

The extreme N-terminal residues of the mitochondrial ribosomal bL27m proteins reside within the ribosomal peptidyl transferase center (PTC) and are conserved from their bacterial ancestors. Mutation or truncation of the N-terminal region of the yeast Mrp7/bL27m protein did not inhibit protein synthesis but significantly impacted the efficacy of the mitochondrial translational process with respect to yielding proteins competent to assemble into functional oxidative phosphorylation (OXPHOS) enzymes. The requirement for the N-terminal residues of Mrp7/bL27m to support normal mitotranslation was more apparent under respiratory growth. We demonstrate that the N-terminal region of Mrp7/bL27m impacts the environment of the PTC and speculate the bL27m proteins serve to fine-tune and optimize mitoribosomal activity with respect to the downstream fate of the nascent chain.

DOI: https://doi.org/10.1002/1873-3468.14631

BMC Med Genomics. 2023 Apr 24. 16(1): 86

Clinical and genetic characteristics of children with COX20-associated mitochondrial disorder: case report and literature review.

Liqing Chen, Yan Liu.

BACKGROUND: The deficiency of cytochrome c oxidase 20 is a rare autosomal recessive mitochondrial disorder characterized by ataxia, dysarthria, dystonia and sensory neuropathy.CASE PRESENTATION: In this study, we describe a patient from a non-consanguineous family exhibiting developmental delay, ataxia, hypotonia, dysarthria, strabismus, visual impairment and areflexia. An examination of nerve conduction showed a normal result at first but revealed axonal sensory neuropathy later. This situation has not been reported in any literatures. The whole-exome sequencing analysis revealed that the patient harbored compound heterozygous mutations (c.41 A > G and c.259G > T) of the COX20 gene. By literature review, 5 patients carried the same compound heterozygous mutations.
CONCLUSION: COX20 might be considered as a potential gene for the early-onset ataxia and the axonal sensory neuropathy. Our patient exhibited strabismus and visual impairment, which expands the clinical presentation of COX20 related mitochondrial disorders caused by the compound heterozygous variants (c.41 A > G and c.259G > T). However, a clear genotype/phenotype correlation has not yet been established. Additional researches and cases are needed to further confirm the correlation.

Keywords: COX20; Case report; Sensory neuropathy; Visual impairment; ataxia

DOI: https://doi.org/10.1186/s12920-023-01513-y

J Fungi (Basel). 2023 Apr 05. pii: 445. [Epub ahead of print]9(4):

A Correlation between 3'-UTR of OXA1 Gene and Yeast Mitochondrial Translation.

Maryam Hajikarimlou, Mohsen Hooshyar, Noor Sunba, Nazila Nazemof, Mohamed Taha Moutaoufik, Sadhena Phanse, Kamaledin B Said, Mohan Babu, Martin Holcik, Bahram Samanfar, Myron Smith, Ashkan Golshani.

Mitochondria possess their own DNA (mtDNA) and are capable of carrying out their transcription and translation. Although protein synthesis can take place in mitochondria, the majority of the proteins in mitochondria have nuclear origin. 3' and 5' untranslated regions of mRNAs (3'-UTR and 5'-UTR, respectively) are thought to play key roles in directing and regulating the activity of mitochondria mRNAs. Here we investigate the association between the presence of 3'-UTR from OXA1 gene on a prokaryotic reporter mRNA and mitochondrial translation in yeast. OXA1 is a nuclear gene that codes for mitochondrial inner membrane insertion protein and its 3'-UTR is shown to direct its mRNA toward mitochondria. It is not clear, however, if this mRNA may also be translated by mitochondria. In the current study, using a β-galactosidase reporter gene, we provide genetic evidence for a correlation between the presence of 3'-UTR of OXA1 on an mRNA and mitochondrial translation in yeast.

Keywords: gene expression; messenger RNA; mitochondria; translation; untranslated regions; yeast

DOI: https://doi.org/10.3390/jof9040445

J Mol Biol. 2023 Apr 25. pii: S0022-2836(23)00199-7. [Epub ahead of print] 168129

The MitoLuc Assay System for Accurate Real-Time Monitoring of Mitochondrial Protein Import within Mammalian Cells.

Hope I Needs, James S Lorriman, Gonçalo C Pereira, Jeremy M Henley, Ian Collinson.

Mitochondrial protein import is critical for organelle biogenesis, bioenergetic function and health. The mechanism of which is poorly understood, particularly of the mammalian system. To address this problem we have established an assay to quantitatively monitor mitochondrial import inside mammalian cells. The reporting is based on a split luciferase, whereby the large fragment is segregated in the mitochondrial matrix and the small complementary fragment is fused to the C-terminus of a purified recombinant precursor protein destined for import. Following import the complementary fragments combine to form an active luciferase-providing a sensitive, accurate and continuous measure of protein import. This advance allows detailed mechanistic examination of the transport process in live cells, including the analysis of import breakdown associated with disease, and high-throughput drug screening. Furthermore, the set-up has the potential to be adapted for the analysis of alternative transport systems within different cell types, and multicellular model organisms.

Keywords: in-cell assay; kinetic analysis; mitochondria; protein import; split luciferase

DOI: https://doi.org/10.1016/j.jmb.2023.168129

PLoS One. 2023 ;18(4): e0284541

MTSviewer: A database to visualize mitochondrial targeting sequences, cleavage sites, and mutations on protein structures.

Andrew N Bayne, Jing Dong, Saeid Amiri, Sali M K Farhan, Jean-François Trempe.

Mitochondrial dysfunction is implicated in a wide array of human diseases ranging from neurodegenerative disorders to cardiovascular defects. The coordinated localization and import of proteins into mitochondria are essential processes that ensure mitochondrial homeostasis. The localization and import of most mitochondrial proteins are driven by N-terminal mitochondrial targeting sequences (MTS's), which interact with import machinery and are removed by the mitochondrial processing peptidase (MPP). The recent discovery of internal MTS's-those which are distributed throughout a protein and act as import regulators or secondary MPP cleavage sites-has expanded the role of both MTS's and MPP beyond conventional N-terminal regulatory pathways. Still, the global mutational landscape of MTS's remains poorly characterized, both from genetic and structural perspectives. To this end, we have integrated a variety of tools into one harmonized R/Shiny database called MTSviewer (https://neurobioinfo.github.io/MTSvieweR/), which combines MTS predictions, cleavage sites, genetic variants, pathogenicity predictions, and N-terminomics data with structural visualization using AlphaFold models of human and yeast mitochondrial proteomes. Using MTSviewer, we profiled all MTS-containing proteins across human and yeast mitochondrial proteomes and provide multiple case studies to highlight the utility of this database.

DOI: https://doi.org/10.1371/journal.pone.0284541