Comparative biochemical studies of ATPases in cells from patients with theT8993G or T8993C mitochondrial DNA mutations

We performed comparative biochemical studies in cultured fibroblast mitocho ndria from patients with the T8993G or the T8993C point mutations in the AT Pase 6 gene of mitochondrial DNA. We found that ATP production was much mor e severely decreased in cells from patients with the T8993G mutation than i n those from patients with the T8993C mutation. Kinetic studies suggest tha t both mutations affect only the F-0 sector of the mitochondrial ATPase com plex. We conclude that these two mutations, which result in the substitutio n of different amino acids at the same site of the ATPase, result in an enz yme with different biochemical characteristics.