title: The role of DMQ(9) in the long-lived mutant clk-1.
abstract: BACKGROUND
  Ubiquinone (UQ) is a redox active lipid that transfers electrons from complex I or II to complex III in the electron transport chain (ETC). The long-lived Caenorhabditis elegans mutant clk-1 is unable to synthesize its native ubiquinone, and accumulates high amounts of its precursor, 5-demethoxyubiquinone-9 (DMQ(9)). In clk-1, complexes I-III activity is inhibited while complexes II-III activity is normal. We asked whether the complexes I-III defect in clk-1 was caused by: (1) a defect in the ETC; (2) an inhibitory effect of DMQ(9); or (3) a decreased amount of ubiquinone.
  
  
  METHODS
  We extracted the endogenous quinones from wildtype (N2) and clk-1 mitochondria, replenished them with exogenous ubiquinones, and measured ETC activities.
  
  
  RESULTS
  Replenishment of extracted mutant and wildtype mitochondria resulted in equal enzymatic activities for complexes I-III and II-III ETC assays. Blue native gels showed that supercomplex formation was indistinguishable between clk-1 and N2. The addition of a pentane extract from clk-1 mitochondria containing DMQ(9) to wildtype mitochondria specifically inhibited complexes I-III activity. UQ in clk-1 mitochondria was oxidized compared to N2.
  
  
  CONCLUSIONS
  Our results show that no measurable intrinsic ETC defect exists in clk-1 mitochondria. The data indicate that DMQ(9) specifically inhibits electron transfer from complex I to ubiquinone.
authors: Department of Genetics, Case Western Reserve University, Cleveland, OH, United States. yyy4@uw.edu
authors: Yu-Ying
authors: YY
authors: Yang
authors: Valeria
authors: V
authors: Vasta
authors: Sihoun
authors: S
authors: Hahn
authors: Jon A
authors: JA
authors: Gangoiti
authors: Elyce
authors: E
authors: Opheim
authors: Margaret M
authors: MM
authors: Sedensky
authors: Phil G
authors: PG
authors: Morgan
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D045222:Electron Transport Chain Complex Proteins / Q000235:genetics / Q000378:metabolism; D008136:Longevity / Q000502:physiology*; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D014451:Ubiquinone / Q000031:analogs & derivatives* / Q000235:genetics / Q000378:metabolism
chemical_list: C104339:CLK-1 protein, C elegans; D029742:Caenorhabditis elegans Proteins; D045222:Electron Transport Chain Complex Proteins; D014451:Ubiquinone; C000866:5-demethoxyubiquinone-9