title: Diversity and origin of alternative NADH:ubiquinone oxidoreductases.
abstract: Mitochondria from various organisms, especially plants, fungi and many bacteria contain so-called alternative NADH:ubiquinone oxidoreductases that catalyse the same redox reaction as respiratory chain complex I, but do not contribute to the generation of transmembrane proton gradients. In eucaryotes, these enzymes are associated with the mitochondrial inner membrane, with their NADH reaction site facing either the mitochondrial matrix (internal alternative NADH:ubiquinone oxidoreductases) or the cytoplasm (external alternative NADH:ubiquinone oxidoreductases). Some of these enzymes also accept NADPH as substrate, some require calcium for activity. In the past few years, the characterisation of several alternative NADH:ubiquinone oxidoreductases on the DNA and on the protein level, of substrate specificities, mitochondrial import and targeting to the mitochondrial inner membrane has greatly improved our understanding of these enzymes. The present review will, with an emphasis on yeast model systems, illuminate various aspects of the biochemistry of alternative NADH:ubiquinone oxidoreductases, address recent developments and discuss some of the questions still open in the field.
authors.affiliation: Universitätsklinkum Frankfurt, Institut für Biochemie I, ZBC, Theodor-Stern-Kai 7, Haus 25B, D-60590, Frankfurt am Main, Germany. kerscher@zbc.klinik.uni-frankfurt.de
authors.forename: S J
authors.initials: SJ
authors.lastname: Kerscher
mesh_terms: D000595:Amino Acid Sequence; D001419:Bacteria; D002462:Cell Membrane / Q000201:enzymology; D017124:Conserved Sequence; D042967:Electron Transport Complex I; D005057:Eukaryotic Cells / Q000201:enzymology; D019143:Evolution, Molecular; D005658:Fungi; D007425:Intracellular Membranes / Q000201:enzymology; D008928:Mitochondria / Q000201:enzymology; D008969:Molecular Sequence Data; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics*; D010944:Plants; D011387:Prokaryotic Cells / Q000201:enzymology; D016415:Sequence Alignment; D013379:Substrate Specificity
chemical_list: D009247:NADH, NADPH Oxidoreductases; D042967:Electron Transport Complex I