The function of respiratory complex I in plants and in human disease

Maclean, Andrew (2017) The function of respiratory complex I in plants and in human disease. Doctoral thesis, University of East Anglia.

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    Complex I is the largest complex in the mitochondrial respiratory chain. Defects in complex I are a major cause of mitochondrial disease in humans. Mutations in the assembly factor NUBPL have been implicated in causing complex I deficiency. To assign pathogenicity to patient NUBPL variants, I used a yeast model, Yarrowia lipolytica, and recreated the corresponding amino acid changes in the Ind1 homolog. Using a combination of BN-PAGE, Western blotting and enzymatic analysis I was able to assign pathogenicity to four of the six variants as well as furthering our understanding of the role of Ind1 in complex I assembly.

    Complex I has been lost in the course of evolution in several unicellular eukaryotes, but never in multicellular eukaryotes. Recently, two studies found that the mitochondrial genes encoding complex I subunits were lacking in the genus Viscum. To investigate if complex I has been lost, I isolated mitochondria from European Mistletoe, Viscum album. My results from BN-PAGE and proteomic analysis indicate that complex I has been lost.

    Complex I requires FeS clusters, which are delivered by the mitochondrial ISC pathway. To better understand this process in plants, I characterised the role of FeS carrier proteins NFU4, NFU5 and GRXS15 in Arabidopsis thaliana. NFU4 and NFU5 were found to be genetically redundant but when combined as a double mutant were embryo lethal. This suggest that NFU4 and NFU5 play an important role in FeS assembly. Mutants in GRXS15 had a severe growth phenotype, but normal levels of respiratory complexes, suggesting GRXS15 plays a secondary role in FeS cluster assembly.

    Understanding complex I will be important in the future for helping to treat human mitochondrial disorders. In addition, studying complex I in plants, including in non-model organisms, helps further our understanding of its function and evolution.

    Item Type: Thesis (Doctoral)
    Faculty \ School: Faculty of Science > School of Biological Sciences
    Depositing User: Megan Ruddock
    Date Deposited: 23 Mar 2018 15:08
    Last Modified: 23 Mar 2018 15:10

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