Proteins with different evolutionary histories now do the same job
(PHYSorg.com Biology)

Mitochondria are essential organelles of cells with a nucleus - known as eukaryotic cells. These are the cells which make up fungi, plants, and animals including humans. Mitochondria work like tiny power plants, processing the energy produced by the digestion of nutrients into a form the cell can use. Yet they have a number of other functions - which are the focus of research by the working group headed by Professor Doron Rapaport at the University of Tübingen`s Interfaculty Institute of Biochemistry.