Leber hereditary optic neuropathy mutations in the ND6 subunit of mitochondrial complex I affect ubiquinone reduction kinetics in a bacterial model of the enzyme

2007 ◽  
Vol 409 (1) ◽  
pp. 129-137 ◽  
Author(s):  
Jukka Pätsi ◽  
Marko Kervinen ◽  
Moshe Finel ◽  
Ilmo E. Hassinen

LHON (Leber hereditary optic neuropathy) is a maternally inherited disease that leads to sudden loss of central vision at a young age. There are three common primary LHON mutations, occurring at positions 3460, 11778 and 14484 in the human mtDNA (mitochondrial DNA), leading to amino acid substitutions in mitochondrial complex I subunits ND1, ND4 and ND6 respectively. We have now examined the effects of ND6 mutations on the function of complex I using the homologous NuoJ subunit of Escherichia coli NDH-1 (NADH:quinone oxidoreductase) as a model system. The assembly level of the NDH-1 mutants was assessed using electron transfer from deamino-NADH to the ‘shortcut’ electron acceptor HAR (hexammine ruthenium), whereas ubiquinone reductase activity was determined using DB (decylubiquinone) as a substrate. Mutant growth in minimal medium with malate as the main carbon source was used for initial screening of the efficiency of energy conservation by NDH-1. The results indicated that NuoJ-M64V, the equivalent of the common LHON mutation in ND6, had a mild effect on E. coli NDH-1 activity, while nearby mutations, particularly NuoJ-Y59F, NuoJ-V65G and NuoJ-M72V, severely impaired the DB reduction rate and cell growth on malate. NuoJ-Met64 and NuoJ-Met72 position mutants lowered the affinity of NDH-1 for DB and explicit C-type inhibitors, whereas NuoJ-Y59C displayed substrate inhibition by oxidized DB. The results are compatible with the notion that the ND6 subunit delineates the binding cavity of ubiquinone substrate, but does not directly take part in the catalytic reaction. How these changes in the enzyme's catalytic properties contribute to LHON pathogenesis is discussed.

2018 ◽  
Vol 120 ◽  
pp. 89-97 ◽  
Author(s):  
Ester López-Gallardo ◽  
Sonia Emperador ◽  
Carmen Hernández-Ainsa ◽  
Julio Montoya ◽  
M. Pilar Bayona-Bafaluy ◽  
...  

1996 ◽  
Vol 313 (1) ◽  
pp. 327-334 ◽  
Author(s):  
Mauro ESPOSTI DEGLI ◽  
Anna NGO ◽  
Gabrielle L. McMULLEN ◽  
Anna GHELLI ◽  
Francesca SPARLA ◽  
...  

We report the first detailed study on the ubiquinone (coenzyme Q; abbreviated to Q) analogue specificity of mitochondrial complex I, NADH:Q reductase, in intact submitochondrial particles. The enzymic function of complex I has been investigated using a series of analogues of Q as electron acceptor substrates for both electron transport activity and the associated generation of membrane potential. Q analogues with a saturated substituent of one to three carbons at position 6 of the 2,3-dimethoxy-5-methyl-1,4-benzoquinone ring have the fastest rates of electron transport activity, and analogues with a substituent of seven to nine carbon atoms have the highest values of association constant derived from NADH:Q reductase activity. The rate of NADH:Q reductase activity is potently but incompletely inhibited by rotenone, and the residual rotenone-insensitive rate is stimulated by Q analogues in different ways depending on the hydrophobicity of their substituent. Membrane potential measurements have been undertaken to evaluate the energetic efficiency of complex I with various Q analogues. Only hydrophobic analogues such as nonyl-Q or undecyl-Q show an efficiency of membrane potential generation equivalent to that of endogenous Q. The less hydrophobic analogues as well as the isoprenoid analogue Q-2 are more efficient as substrates for the redox activity of complex I than for membrane potential generation. Thus the hydrophilic Q analogues act also as electron sinks and interact incompletely with the physiological Q site in complex I that pumps protons and generates membrane potential.


2021 ◽  
Vol 12 ◽  
Author(s):  
Martin Engvall ◽  
Aki Kawasaki ◽  
Valerio Carelli ◽  
Rolf Wibom ◽  
Helene Bruhn ◽  
...  

Leber hereditary optic neuropathy (LHON) is a mitochondrial disease causing severe bilateral visual loss, typically in young adults. The disorder is commonly caused by one of three primary point mutations in mitochondrial DNA, but a number of other rare mutations causing or associated with the clinical syndrome of LHON have been reported. The mutations in LHON are almost exclusively located in genes encoding subunits of complex I in the mitochondrial respiratory chain. Here we report two patients, a mother and her son, with the typical LHON phenotype. Genetic investigations for the three common mutations were negative, instead we found a new and previously unreported mutation in mitochondrial DNA. This homoplasmic mutation, m.13345G>A, is located in the MT-ND5 gene, encoding a core subunit in complex I in the mitochondrial respiratory chain. Investigation of the patients mitochondrial respiratory chain in muscle found a mild defect in the combined activity of complex I+III. In the literature six other mutations in the MT-ND5 gene have been associated with LHON and by this report a new putative mutation in the MT-ND5 can be added.


2005 ◽  
Vol 62 (5) ◽  
pp. 730 ◽  
Author(s):  
Alessandra Baracca ◽  
Giancarlo Solaini ◽  
Gianluca Sgarbi ◽  
Giorgio Lenaz ◽  
Agostino Baruzzi ◽  
...  

2011 ◽  
Vol 437 (2) ◽  
pp. e1-e3 ◽  
Author(s):  
Judy Hirst

The prokaryotic and eukaryotic homologues of complex I (proton-pumping NADH:quinone oxidoreductase) perform the same function in energy transduction, but the eukaryotic enzymes are twice as big as their prokaryotic cousins, and comprise three times as many subunits. Fourteen core subunits are conserved in all complexes I, and are sufficient for catalysis – so why are the eukaryotic enzymes embellished by so many supernumerary or accessory subunits? In this issue of the Biochemical Journal, Angerer et al. have provided new evidence to suggest that the supernumerary subunits are important for enzyme stability. This commentary aims to put this suggestion into context.


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