Involved in mitochondrial biogenesis and G2/M phase cell cycle progression. Component of the mitochondrial ribosome large subunit (39S) which comprises a 16S rRNA and about 50 distinct proteins. Ubiquitously expressed (at protein level). Expressed both maternally and zygotically. Expressed throughout embryogenesis. Flies do not grow after hatching, moved slowly and died as first instar larvae. Belongs to the mitochondrion-specific ribosomal protein mL55 family.