Major helicase player in mitochondrial RNA metabolism and maintenance. Likely component of the mitochondrial degradosome (mtEXO) complex, that degrades 3' overhang double-stranded RNA with a 3'-to-5' directionality in an ATP-dependent manner. ATPase and ATP-dependent multisubstrate helicase, able to unwind double-stranded (ds) DNA and RNA, and RNA/DNA heteroduplexes in the 5'-to-3' direction. Regulates mRNA stability and is required for the correct processing and maturation of mitochondrial transcripts. ATP + H2O = ADP + H(+) + phosphate Unlike in mammals, does not localize to the nucleus. Belongs to the helicase family.