Binds promoter DNA and regulates initiation of transcription. Required for normal mitochondrial transcription and translation, and for normal assembly of mitochondrial respiratory complexes. Required for normal mitochondrial function. Maintains 16S rRNA levels and functions in mitochondrial ribosome assembly by regulating the biogenesis of the 39S ribosomal subunit (By similarity). Contains seven structural repeats of about 35 residues, where each repeat contains three helices. The repeats form a superhelical structure with a solenoid shape (By similarity). Belongs to the mTERF family.