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Highly divergent mitochondrial ATP synthase complexes in Tetrahymena thermophila
Journal article   Open access

Highly divergent mitochondrial ATP synthase complexes in Tetrahymena thermophila

Praveen Balabaskaran Nina, Natalya V Dudkina, Lesley A Kane, Jennifer E van Eyk, Egbert J Boekema, Michael W Mather and Akhil B Vaidya
PLoS biology, v 8(7), pp e1000418-e1000418
13 Jul 2010
PMID: 20644710
url
https://doi.org/10.1371/journal.pbio.1000418View
Published, Version of Record (VoR) Open

Abstract

Amino Acid Sequence Tetrahymena thermophila - genetics Models, Molecular Molecular Sequence Data Multienzyme Complexes - genetics Phylogeny Tetrahymena thermophila - drug effects Mitochondrial Proton-Translocating ATPases - chemistry Tetrahymena thermophila - enzymology Protein Subunits - metabolism Adenosine Diphosphate - pharmacology Multienzyme Complexes - chemistry Mitochondrial Proton-Translocating ATPases - genetics Oxidative Phosphorylation - drug effects Sequence Alignment Genetic Variation - drug effects Oxygen Consumption - drug effects Mass Spectrometry Chromatography, Liquid Conserved Sequence Protein Subunits - chemistry Evolution, Molecular
The F-type ATP synthase complex is a rotary nano-motor driven by proton motive force to synthesize ATP. Its F(1) sector catalyzes ATP synthesis, whereas the F(o) sector conducts the protons and provides a stator for the rotary action of the complex. Components of both F(1) and F(o) sectors are highly conserved across prokaryotes and eukaryotes. Therefore, it was a surprise that genes encoding the a and b subunits as well as other components of the F(o) sector were undetectable in the sequenced genomes of a variety of apicomplexan parasites. While the parasitic existence of these organisms could explain the apparent incomplete nature of ATP synthase in Apicomplexa, genes for these essential components were absent even in Tetrahymena thermophila, a free-living ciliate belonging to a sister clade of Apicomplexa, which demonstrates robust oxidative phosphorylation. This observation raises the possibility that the entire clade of Alveolata may have invented novel means to operate ATP synthase complexes. To assess this remarkable possibility, we have carried out an investigation of the ATP synthase from T. thermophila. Blue native polyacrylamide gel electrophoresis (BN-PAGE) revealed the ATP synthase to be present as a large complex. Structural study based on single particle electron microscopy analysis suggested the complex to be a dimer with several unique structures including an unusually large domain on the intermembrane side of the ATP synthase and novel domains flanking the c subunit rings. The two monomers were in a parallel configuration rather than the angled configuration previously observed in other organisms. Proteomic analyses of well-resolved ATP synthase complexes from 2-D BN/BN-PAGE identified orthologs of seven canonical ATP synthase subunits, and at least 13 novel proteins that constitute subunits apparently limited to the ciliate lineage. A mitochondrially encoded protein, Ymf66, with predicted eight transmembrane domains could be a substitute for the subunit a of the F(o) sector. The absence of genes encoding orthologs of the novel subunits even in apicomplexans suggests that the Tetrahymena ATP synthase, despite core similarities, is a unique enzyme exhibiting dramatic differences compared to the conventional complexes found in metazoan, fungal, and plant mitochondria, as well as in prokaryotes. These findings have significant implications for the origins and evolution of a central player in bioenergetics.

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Collaboration types
Domestic collaboration
International collaboration
Web of Science research areas
Biochemistry & Molecular Biology
Biology
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