Application of the obligate aerobic yeast Yarrowia lipolytica as a eucaryotic model to analyse Leigh syndrome mutations in the complex I core subunits PSST and TYKY.

We have used the obligate aerobic yeast Yarrowia lipolytica to reconstruct and analyse three missense mutations in the nuclear coded subunits homologous to bovine TYKY and PSST of mitochondrial complex I (proton translocating NADH:ubiquinone oxidoreductase) that have been shown to cause Leigh syndrome (MIM 25600), a severe progressive neurodegenerative disorder. While homozygosity for a V122M substitution in NDUFS7 (PSST) has been found in two siblings with neuropathologically proven Leigh syndrome (R. Triepels et al., Ann. Neurol. 45 (1999) 787), heterozygosity for a P79L and a R102H substitution in NDUFS8 (TYKY) has been found in another patient (J. Loeffen et al., Am. J. Hum. Genet. 63 (1998) 1598). Mitochondrial membranes from Y. lipolytica strains carrying any of the three point mutations exhibited similar complex I defects, with V(max) being reduced by about 50%. This suggests that complex I mutations that clinically present as Leigh syndrome may share common characteristics. In addition changes in the K(m) for n-decyl-ubiquinone and I(50) for hydrophobic complex I inhibitors were observed, which provides further evidence that not only the hydrophobic, mitochondrially coded subunits, but also some of the nuclear coded subunits of complex I are involved in its reaction with ubiquinone.