text: Protofection is a developing technique and is continuously being improved. A specific protein transduction system has been created that is complexed with mtDNA, which enables the mtDNA to move across the targeted cell's membrane and specifically target mitochondria. The transduction system used consists of a protein transduction domain, mitochondrial localization sequences, and mitochondrial transcription factor A. Each of these play a specific role in protofection:
  * A protein transduction domain is needed because they are small regions of proteins that can cross the cell membrane of cells, independently.
  * A specific mitochondrial localization sequences is used for protofection because it permits mtDNA to enter the mitochondria. 
  * Mitochondrial transcription factor A is used because it unwinds the mtDNA that enters the mitochondria, which is critical for mtDNA replication. 
  This process can lead to an increase in the amount of mtDNA present in the mitochondria of the target cells.
  The transduction system has been tweaked and modified, since the first use of protofection. To shorten the name of the complex, which was previously called PTD-MLS-TFAM complex, it is now named MTD-TFAM. MTD stands for mitochondrial transduction domain and it includes the protein transduction domain and the mitochondrial localization sequences.