Mitochondrial gene expression is essential in all organisms. Our understanding of mitochondrial transcription on a biochemical level has been limited by the inability to purify the individual protein components involved in mitochondrial gene expression. Recently, new systems have been identified that permit purification of these proteins from bacteria. However, the generalizability of these systems is not clear. Here, we have applied the technology from the Cameron lab to express and purify mitochondrial RNA polymerase and transcription factor A from Drosophila melanogaster . We show that the use of SUMO system to produce SUMO fusion proteins in bacteria is effective not only for the human and mouse proteins, but also for the fl y proteins. The application of this system to produce the mitochondrial proteins from other organisms should permit detailed understanding of mitochondrial transcription from any organism.