Respiration-deficient Chinese hamster cell mutants: Biochemical characterization

Abstract

We have previously classified 35 of our respiration-deficient mutants into seven complementation groups and one “overlapping” mutant which does not complement mutants from groups I and II. In this paper we report on the biochemical characterization of representatives of complementation groups I, II, VII, and the “overlapping” mutant. We show that these mutants all have a defect in complex I of the electron-transport chain. The general features of these mutants are: (1) a low rate of O₂ consumption in whole cells; (2) a low rate of release of¹⁴CO₂ from [2-¹⁴C]pyruvate, [1-¹⁴C]pyruvate, and [3-¹⁴ C]β-hydroxybutyrate; (3) a low rate of release of¹⁴CO₂ from [5-¹⁴C]glutamate and [1-¹⁴C]glutamate in mutants from groups II, VII, and the “overlapping” mutant, whereas a significant amount of¹⁴CO₂ is released in mutants from group I; (4) a substantial rate of release of¹⁴CO₂ from [U-¹⁴C]aspartate; (5) in isolated mitochondria, succinate and α-glycerol phosphate stimulate O₂ consumption whereas substrates which generate NADH, such as malate, do not; and (6) there is little or no rotenone-sensitive NADH oxidase activity in isolated mitochondria.