title: An essential bacterial-type cardiolipin synthase mediates cardiolipin formation in a eukaryote.
abstract: Cardiolipin is important for bacterial and mitochondrial stability and function. The final step in cardiolipin biosynthesis is catalyzed by cardiolipin synthase and differs mechanistically between prokaryotes and eukaryotes. To study the importance of cardiolipin synthesis for mitochondrial integrity, membrane protein complex formation, and cell proliferation in the human and animal pathogenic protozoan parasite, Trypanosoma brucei, we generated conditional cardiolipin synthase-knockout parasites. We found that cardiolipin formation in T. brucei procyclic forms is catalyzed by a bacterial-type cardiolipin synthase, providing experimental evidence for a prokaryotic-type cardiolipin synthase in a eukaryotic organism. Ablation of enzyme expression resulted in inhibition of de novo cardiolipin synthesis, reduction in cellular cardiolipin levels, alterations in mitochondrial morphology and function, and parasite death in culture. By using immunofluorescence microscopy and blue-native gel electrophoresis, cardiolipin synthase was shown to colocalize with inner mitochondrial membrane proteins and to be part of a large protein complex. During depletion of cardiolipin synthase, the levels of cytochrome oxidase subunit IV and cytochrome c1, reflecting mitochondrial respiratory complexes IV and III, respectively, decreased progressively.
authors.affiliation: Institute of Biochemistry and Molecular Medicine,  University of Bern, 3012 Bern,  Switzerland.
authors.forename: Mauro
authors.initials: M
authors.lastname: Serricchio
authors.forename: Peter
authors.initials: P
authors.lastname: Bütikofer
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001419:Bacteria / Q000201:enzymology; D002308:Cardiolipins / Q000096:biosynthesis*; D003575:Cytochromes c1 / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D005057:Eukaryotic Cells / Q000201:enzymology; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism; D051336:Mitochondrial Membranes / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D017386:Sequence Homology, Amino Acid; D017855:Transferases (Other Substituted Phosphate Groups) / Q000235:genetics / Q000378:metabolism*; D014346:Trypanosoma brucei brucei / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
chemical_list: D002308:Cardiolipins; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D015800:Protozoan Proteins; D049452:Green Fluorescent Proteins; D003575:Cytochromes c1; D003576:Electron Transport Complex IV; D017855:Transferases (Other Substituted Phosphate Groups); C100091:cardiolipin synthetase