bims-cytox1 2020-09-13 papers

Issue of 2020–09–13
three papers selected by
Gavin McStay, Staffordshire University

Microb Cell. 2020 Jun 30. 7(9): 234-249

Systematic analysis of nuclear gene function in respiratory growth and expression of the mitochondrial genome in S. cerevisiae.

Maria Stenger, Duc Tung Le, Till Klecker, Benedikt Westermann.

The production of metabolic energy in form of ATP by oxidative phosphorylation depends on the coordinated action of hundreds of nuclear-encoded mitochondrial proteins and a handful of proteins encoded by the mitochondrial genome (mtDNA). We used the yeast Saccharomyces cerevisiae as a model system to systematically identify the genes contributing to this process. Integration of genome-wide high-throughput growth assays with previously published large data sets allowed us to define with high confidence a set of 254 nuclear genes that are indispensable for respiratory growth. Next, we induced loss of mtDNA in the yeast deletion collection by growth on ethidium bromide-containing medium and identified twelve genes that are essential for viability in the absence of mtDNA (i.e. petite-negative). Replenishment of mtDNA by cytoduction showed that respiratory-deficient phenotypes are highly variable in many yeast mutants. Using a mitochondrial genome carrying a selectable marker, ARG8 m , we screened for mutants that are specifically defective in maintenance of mtDNA and mitochondrial protein synthesis. We found that up to 176 nuclear genes are required for expression of mitochondria-encoded proteins during fermentative growth. Taken together, our data provide a comprehensive picture of the molecular processes that are required for respiratory metabolism in a simple eukaryotic cell.

Keywords: mitochondria; mitochondrial DNA; oxidative phosphorylation; petite mutant; yeast

DOI: https://doi.org/10.15698/mic2020.09.729

Structure. 2020 Sep 03. pii: S0969-2126(20)30290-2. [Epub ahead of print]

NMR Structure and Dynamics Studies of Yeast Respiratory Supercomplex Factor 2.

Shu Zhou, Pontus Pettersson, Jingjing Huang, Peter Brzezinski, Régis Pomès, Lena Mäler, Pia Ädelroth.

The Saccharomyces cerevisiae respiratory supercomplex factor 2 (Rcf2) is a 224-residue protein located in the mitochondrial inner membrane where it is involved in the formation of supercomplexes composed of cytochrome bc1 and cytochrome c oxidase. We previously demonstrated that Rcf2 forms a dimer in dodecylphosphocholine micelles, and here we report the solution NMR structure of this Rcf2 dimer. Each Rcf2 monomer has two soluble α helices and five putative transmembrane (TM) α helices, including an unexpectedly charged TM helix at the C terminus, which mediates dimer formation. The NOE contacts indicate the presence of inter-monomer salt bridges and hydrogen bonds at the dimer interface, which stabilize the Rcf2 dimer structure. Moreover, NMR chemical shift change mapping upon lipid titrations as well as molecular dynamics analysis reveal possible structural changes upon embedding Rcf2 into a native lipid environment. Our results contribute to the understanding of respiratory supercomplex formation and regulation.

Keywords: Hig protein; charge zipper; membrane protein; mitochondria; molecular dynamics; protein-lipid interactions; solution structure

DOI: https://doi.org/10.1016/j.str.2020.08.008

Rev Neurosci. 2020 Sep 09. pii: /j/revneuro.ahead-of-print/revneuro-2020-0034/revneuro-2020-0034.xml. [Epub ahead of print]

Treatment for mitochondrial diseases.

Tongling Liufu, Zhaoxia Wang.

Mitochondrial diseases are predominantly caused by mutations of mitochondrial or nuclear DNA, resulting in multisystem defects. Current treatments are largely supportive, and the disorders progress relentlessly. Nutritional supplements, pharmacological agents and physical therapies have been used in different clinical trials, but the efficacy of these interventions need to be further evaluated. Several recent reviews discussed some of the interventions but ignored bias in those trials. This review was conducted to discover new studies and grade the original studies for potential bias with revised Cochrane Collaboration guidelines. We focused on seven published studies and three unpublished studies; eight of these studies showed improvement in outcome measurements. In particular, two of the interventions have been tested in studies with strict design, which we believe deserve further clinical trials with a large sample. Additionally, allotopic expression of the ND4 subunit seemed to be an effective new treatment for patients with Leber hereditary optic neuropathy.

Keywords: mitochondrial diseases; nutritional supplements; pharmacological agents; physical therapies

DOI: https://doi.org/10.1515/revneuro-2020-0034