NADH dehydrogenase of Trypanosoma brucei is important for efficient acetate production in bloodstream forms.

In the slender bloodstream form, Trypanosoma brucei mitochondria are repressed for many functions. Multiple components of mitochondrial complex I, NADH:ubiquinone oxidoreductase, are expressed in this stage, but electron transfer through complex I is not essential. Here we investigate the role of the parasite's second NADH:ubiquinone oxidoreductase, NDH2, which is composed of a single subunit that also localizes to the mitochondrion.

Enigmatic presence of mitochondrial complex I in Trypanosoma brucei bloodstream forms.

The presence of mitochondrial respiratory complex I in the pathogenic bloodstream stages of Trypanosoma brucei has been vigorously debated: increased expression of mitochondrially encoded functional complex I mRNAs is countered by low levels of enzymatic activity that show marginal inhibition by the specific inhibitor rotenone. We now show that epitope-tagged versions of multiple complex I subunits assemble into α and β subcomplexes in the bloodstream stage and that these subcomplexes require the mitochondrial genome for their assembly. Despite the presence of these large (740- and 855-kDa) multisubunit complexes, the electron transport activity of complex I is not essential under experimental conditions since null mutants of two core genes (NUBM and NUKM) showed no growth defect in vitro or in mouse infection.