Component of the mitochondrial ribosome large subunit (39S) which comprises a 16S rRNA and about 50 distinct proteins. Component of the mitochondrial ribosome small subunit (28S) which comprises a 12S rRNA and about 30 distinct proteins. Belongs to the mitochondrion-specific ribosomal protein mL42 family. Has been found in the mitochondrial ribosome large and small subunits.