A respiration-deficient Chinese hamster cell line with a defect in NADH-coenzyme Q reductase

We have recently described a Chinese hamster cell line with a greatly reduced rate of respiration. In this report we conclude that the defects is in NADH-coenzyme Q reductase (NADH oxidase), the first part of the electron transport chain. The conclusion is based on the following observations. (a) In this and in the earlier report we determined that the relevant enzymes of the Krebs cycle are present and active. (b) Oxygen consumption by isolated mitochondria is normal when driven by succinate and alpha-glycerolphosphate. (c) Difference spectra between reduced and oxidized forms indicate that all cytochromes are present and functional. (d) In contrast, substrates such as malate, glutamate, alpha-ketoglutarate, and isocitrate which generate NADH do not stimulate oxygen consumption in mutant mitochondria. (e) A direct assay of the rotenone-sensitive NADH oxidase in Lubrol-treated mitochondria from mutant cells revealed less than one-tenth of the activity when compared with wild type mitochondria. (f) The treatment of wild type cells with rotenone, a specific inhibitor of NADH-CoQ reductase, yielded an exact phenocopy of the mutant by several criteria. This is the first report of a respiration-deficient mammalian cell mutant in tissue culture.