title: Identification of prokaryotic homologues indicates an endosymbiotic origin for the alternative oxidases of mitochondria (AOX) and chloroplasts (PTOX).
abstract: The alternative oxidase is a ubiquinol oxidase that has been found to date in the mitochondrial respiratory chain of plants, some fungi and protists. Because of its sparse distribution among eukaryotic lineages and because of its diversity in regulatory mechanisms, the origin of AOX has been a mystery, particularly since no prokaryotic homologues have previously been identified. Here we report the identification of a gene encoding a clear homologue of the mitochondrial alternative oxidase in an alpha-proteobacterium, and the identification of three cyanobacterial genes that encode clear homologues of the plastid-specific alternative oxidase of plants and algae. These findings suggest that the eukaryotic nuclear genes for the alternative oxidases of mitochondria and chloroplasts were acquired via endosymbiotic gene transfer from the eubacterial ancestors of these two organelles, respectively.
authors.affiliation: Institute of Botany III, Heinrich Heine University of Düsseldorf, Universitätsstrasse 1, D-40225 Düsseldorf, Germany.
authors.forename: Ariane
authors.initials: A
authors.lastname: Atteia
authors.forename: Robert
authors.initials: R
authors.lastname: van Lis
authors.forename: Jaap J
authors.initials: JJ
authors.lastname: van Hellemond
authors.forename: Aloysius G M
authors.initials: AG
authors.lastname: Tielens
authors.forename: William
authors.initials: W
authors.lastname: Martin
authors.forename: Katrin
authors.initials: K
authors.lastname: Henze
mesh_terms: D020561:Alphaproteobacteria / Q000201:enzymology / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D002736:Chloroplasts / Q000187:drug effects / Q000201:enzymology*; D000458:Cyanobacteria / Q000201:enzymology / Q000235:genetics; D019143:Evolution, Molecular; D008928:Mitochondria / Q000201:enzymology*; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000235:genetics*; D010802:Phylogeny; D010940:Plant Proteins; D011387:Prokaryotic Cells / Q000201:enzymology / Q000378:metabolism*; D012457:Salicylamides / Q000494:pharmacology; D017386:Sequence Homology, Amino Acid; D013559:Symbiosis / Q000235:genetics*; D000099188:Alternative Oxidase
chemical_list: D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D012457:Salicylamides; D000099188:Alternative Oxidase; C005703:salicylhydroxamic acid