Mitochondrial carrier family inventory of Trypanosoma brucei brucei: Identification, expression and subcellular localisation

The mitochondrial carrier family (MCF) is a group of structurally conserved proteins that mediate the transport of a wide range of metabolic intermediates across the mitochondrial inner membrane. In this paper, an overview of the mitochondrial carrier proteins (MCPs) of the early-branching kinetoplastid parasite Trypanosoma brucei brucei is presented. Sequence analysis and phylogenetic reconstruction gave insight into the evolution and conservation of the 24 identified TbMCPs; for most of these, putative transport functions could be predicted. Comparison of the kinetoplastid MCP inventory to those previously reported for other eukaryotes revealed remarkable deviations: T. b. brucei lacks genes encoding some prototypical MCF members, such as the citrate carrier and uncoupling proteins. The in vivo expression of the identified TbMCPs in the two replicating life-cycle forms of T. b. brucei, the bloodstream-form and procyclic-form, was quantitatively assessed at the mRNA level by Northern blot analysis. Immunolocalisation studies confirmed that majority of the 24 identified TbMCPs is found in the mitochondrion of procyclic-form T. b. brucei.