Plays an essential role in facilitating the proper assembly of the mitochondrial large ribosomal subunit and its helicase activity is essential for this function. May be involved in RNA processing or transport. Has RNA and Mg(2+)-dependent ATPase activity (By similarity). ATP + H2O = ADP + H(+) + phosphate Monomer. Found in a complex with GRSF1, DHX30, FASTKD2 and FASTKD5. Associates with the 16S mitochondrial rRNA (16S mt-rRNA) and with the mitochondrial ribosome large subunit (39S). Transported between these two compartments. Nuclear localization depends on active RNA polymerase II transcription. Localizes to mitochondrial RNA granules found in close proximity to the mitochondrial nucleoids (By similarity). Belongs to the DEAD box helicase family.