Trypanosoma brucei Mitochondrial Respiratome: Composition and Organization in Procyclic Form

Abstract

The mitochondrial respiratory chain is comprised of four different protein complexes (I-IV), which are responsible for electron transport and generation of proton gradient in the mitochondrial intermembrane space. This proton gradient is then used by F o F 1 -ATP synthase (complex V) to produce ATP by oxidative phosphorylation. In this study, the respiratory complexes I, II, and III were affinity purified from Trypanosoma brucei procyclic form cells and their composition was determined by mass spectrometry. The results along with those that we previously reported for complexes IV and V showed that the respiratome of Trypanosoma is divergent because many of its proteins are unique to this group of organisms. The studies also identified two mitochondrial subunit proteins of respiratory complex IV that are encoded by edited RNAs. Proteomics data from analyses of complexes purified using numerous tagged component proteins in each of the five complexes were used to generate the first predicted protein-protein interaction network of the Trypanosoma brucei respiratory chain. These results provide the first comprehensive insight into the unique composition of the respiratory complexes in Trypanosoma brucei, an early diverged eukaryotic pathogen.

The mitochondrial respiratory chain of the secondary green alga Euglena gracilis shares many additional subunits with parasitic Trypanosomatidae

“…Alternative pathways described in trypanosomes are similar to the alternative pathways described in other protists, green plants and fungi: an alternative oxidase (AOX or TAO), a type-II NADH dehydrogenase (NDA or TAD) (Acestor et al, 2011;Fang and Beattie, 2002) and a glyceraldehyde-3-phosphate dehydrogenase (G3PD), the activity of which compensates for the absence of oxidative phosphorylation during the bloodstream stage (Chaudhuri et al, 2006). Our analyses demonstrated that trypanosomal alternative oxidase and type-II NADH dehydrogenase are homologous to those of the other organisms.…”

“…Most of these 19 proteins were also identified in N. gruberi. Out of the 34 additional CI subunits described in T. brucei as potentially kinetoplastid-specific (Acestor et al, 2011;, we found 14 subunits in E. gracilis (NDTB1,2,5,6,11,12,17,18,22,25,28,29,31 and 34) ( Figure 2). Three of these subunits were also identified in D. papillatum (NDTB26/29/32) and 10 in N.…”

“…Four of the T. cruzi-specific subunits (SDHTC3/6/8/9) and two other additional subunits (SDHTB1/2) have been identified in T. brucei (Acestor et al, 2011). Similarly, we found the canonical SDH1 and SDH2 subunits in E. gracilis (the latter also split in two parts, SDH2N and SDH2C), as well as eight apparently kinetoplastid-specific subunits (SDHTC3/4/6-10 and SDHTB1) (Figure 2).…”

“…In T. brucei, three additional apparently specific subunits (QCRTB1, QCRTB2 and QCRTB3) have been described (Acestor et al, 2011), two of which were found in E. gracilis (QCRTB1/2). Interestingly, we noticed that in the MCL-1.1 run, QCRTB2 fell in an orthologous group of M16 peptidases also containing QCR1 and QCR2.…”

“…On the one hand, an alternative electron transfer chain, composed of a glyceraldehyde-3-phosphate dehydrogenase (G3PD) and an alternative oxidase (TAO or AOX), replaces the classical complexes I-IV during the bloodstream (or mammalianinfective) stage (Chaudhuri et al, 2006). On the other hand, respiratory complexes I-IV and the ATP synthase (complex V) found in the procyclic (or insect-infective) stage of trypanosomes possess many apparently-specific additional subunits (Acestor et al, 2011;Morales et al, 2009;Panigrahi et al, 2008;Zikova et al, 2008;Zikova et al, 2009). …”