Throughout eukaryotes, the gene encoding subunit 6 (ATP6) of the F(1)F(O)-ATP synthase (complex V) is maintained in mitochondrial (mt) genomes, presumably because of its high hydrophobicity due to its incorporation into the membrane-bound F(O) moiety. In Trypanosoma species, a mt transcript that undergoes extensive processing by RNA editing has a very low sequence similarity to ATP6 from other organisms. The notion that the putative ATP6 subunit is assembled into the F(O) sub-complex is ostensibly challenged by the existence of naturally occurring dyskinetoplastic (Dk) and akinetoplastid (Ak) trypanosomes, which are viable despite lacking the mtDNA required for its expression. Taking advantage of the different phenotypes between RNA interference knock-down cell lines in which the expression of proteins involved in mtRNA metabolism and editing can be silenced, we provide support for the view that ATP6 is encoded in the mt genome of Trypanosoma species and that it is incorporated into complex V. The reduction of the F(1)F(O) oligomer of complex V coincides with the accumulation of the F(1) moiety in ATP6-lacking cells, which also appear to lack the F(O) ATP9 multimeric ring. The oligomycin sensitivity of ATPase activity of complex V in ATP6-lacking cells is reduced, reflecting the insensitivity of the Dk and Ak cells to this drug. In addition, the F(1) moiety of complex V appears to exist as a dimer in steady state conditions and contains the ATP4 subunit traditionally assigned to the F(O) sub-complex.

Biology Centre Institute of Parasitology Czech Academy of Sciences and Faculty of Biology University of South Bohemia 37005 Ceské Budejovice Czech Republic

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Cultured bloodstream Trypanosoma brucei adapt to life without mitochondrial translation release factor 1

Integrity of the core mitochondrial RNA-binding complex 1 is vital for trypanosome RNA editing

ATPaseTb2, a unique membrane-bound FoF1-ATPase component, is essential in bloodstream and dyskinetoplastic trypanosomes

Genome and phylogenetic analyses of Trypanosoma evansi reveal extensive similarity to T. brucei and multiple independent origins for dyskinetoplasty

Futile import of tRNAs and proteins into the mitochondrion of Trypanosoma brucei evansi