Development of a tool that permits the efficient “at will” introduction of any foreign nucleic acid into mitochondria by using a protein shuttle. It relies on two major principles: the interaction between a nucleic acid and a protein, and the intra-mitochondrial localization of nuclear-encoded proteins that are addressed to organelles thanks to a targeting sequence. In other words, a protein with a mitochondrial targeting sequence and capable of interacting with a foreign nucleic acid will permit introduction of the later one into the mitochondria by co-import.