Lay summary

Mitochondria do not form de novo but derive from preexisting organelles by processes collectively referred to as mitochondrial biogenesis. These include import of most mitochondrial proteins and, in most eukaryotes, import of at least some tRNAs. Furthermore, a limited set of proteins that is essential for oxidative phosphorylation need to be synthesized inside mitochondria.

My research group is working on mitochondrial biogenesis using the parasitic protozoa Trypanosoma brucei as a model system. T. brucei belongs to a different eukaryotic supergroup than yeast, mammals and most other model organisms in molecular biology. Its mitochondrion therefore shows many pecularities. The most important ones in the context of our studies are a complete lack of mitochondrial tRNA genes that is compensated by import of cytosolic tRNAs and a mitochondrial protein import system that is very different from other eukaryotes. Moreover, T. brucei is the causative agent of human sleeping sickness and therefore of great clinical importance.

 All mitochondria have a double membrane. Thus, tRNAs as well as many proteins needs to be transported across both the outer and inner membrane to reach the matrix, the soluble innermost compartment of mitochondria. In this proposal we focus on the outer membrane of the T. brucei mitochondrion. It is known from other organisms that the outer mitochondrial membrane contains only few dozens of major proteins which include the import machineries for macromolecules. We therefore plan to characterize the outer membrane proteome of T. brucei mitochondria with the ultimate aim to identify the as yet elusive components of the tRNA and protein import machineries.