The mitochondrial respiratory chain and ATP synthase complexes: Composition, structure and mutational studies

The oxidative phosphorylation process is dependent on the assembly of both the respiratory chain that generates the electrochemical potential of the m itochondrial inner membrane and the ATP synthase complex which uses this me mbrane potential to drive ATP synthesis. The five respiratory enzymes invol ved in this process, complexes I to V, are composed of multiple subunits, s ome of which are synthesized on mitochondrial ribosomes, whereas others are a product of the nucleocytoplasmic genetic system. The mitochondrial genom e has a limited coding capacity and the co-ordinate expression of all the s ubunits forming these complexes has been shown to be under nuclear control. Present knowledge of complexes I to V mainly comes from studies of bovine and fungal mitochondria. If beef heart mitochondria represent a choice mate rial for studying the composition and structure of these complexes, Sacchar omyces cerevisiae and Neurospora crassa and their numerous respiratory muta nts, are ideal organisms for investigating the co-ordination of nuclear and mitochondrial genomes in their assembly. The major reason for the interest in respiratory complexes and ATP synthase from the mitochondrial inner mem brane in Homo sapiens and in higher plants is the relationship between enzy me deficiencies and human diseases and ageing on one hand, and such plant p henotypic abnormalities as cytoplasmic male sterility on the other. (C) 199 9 Editions scientifiques et medicales Elsevier SAS.