title: The single mitochondrial porin of Trypanosoma brucei is the main metabolite transporter in the outer mitochondrial membrane.
abstract: All mitochondria have integral outer membrane proteins with beta-barrel structures including the conserved metabolite transporter VDAC (voltage dependent anion channel) and the conserved protein import channel Tom40. Bioinformatic searches of the Trypanosoma brucei genome for either VDAC or Tom40 identified a single open reading frame, with sequence analysis suggesting that VDACs and Tom40s are ancestrally related and should be grouped into the same protein family: the mitochondrial porins. The single T. brucei mitochondrial porin is essential only under growth conditions that depend on oxidative phosphorylation. Mitochondria isolated from homozygous knockout cells did not produce adenosine-triphosphate (ATP) in response to added substrates, but ATP production was restored by physical disruption of the outer membrane. These results demonstrate that the mitochondrial porin identified in T. brucei is the main metabolite channel in the outer membrane and therefore the functional orthologue of VDAC. No distinct Tom40 was identified in T. brucei. In addition to mitochondrial proteins, T. brucei imports all mitochondrial tRNAs from the cytosol. Isolated mitochondria from the VDAC knockout cells import tRNA as efficiently as wild-type. Thus, unlike the scenario in plants, VDAC is not required for mitochondrial tRNA import in T. brucei.
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland.
authors.forename: Mascha
authors.initials: M
authors.lastname: Pusnik
authors.forename: Fabien
authors.initials: F
authors.lastname: Charrière
authors.forename: Pascal
authors.initials: P
authors.lastname: Mäser
authors.forename: Ross F
authors.initials: RF
authors.lastname: Waller
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Dagley
authors.forename: Trevor
authors.initials: T
authors.lastname: Lithgow
authors.forename: André
authors.initials: A
authors.lastname: Schneider
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000818:Animals; D001692:Biological Transport; D019295:Computational Biology; D051336:Mitochondrial Membranes / Q000378:metabolism*; D016366:Open Reading Frames; D010085:Oxidative Phosphorylation; D012313:RNA / Q000378:metabolism; D000077278:RNA, Mitochondrial; D012343:RNA, Transfer / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000737:chemistry* / Q000235:genetics; D050994:Voltage-Dependent Anion Channels / Q000235:genetics* / Q000378:metabolism*
chemical_list: D000077278:RNA, Mitochondrial; D050994:Voltage-Dependent Anion Channels; D012313:RNA; D000255:Adenosine Triphosphate; D012343:RNA, Transfer