Component of the mitochondrial large ribosomal subunit (mt-LSU) (PubMed:28892042, PubMed:25838379, PubMed:25278503). Mature mammalian 55S mitochondrial ribosomes consist of a small (28S) and a large (39S) subunit. The 28S small subunit contains a 12S ribosomal RNA (12S mt-rRNA) and 30 different proteins. The 39S large subunit contains a 16S rRNA (16S mt-rRNA), a copy of mitochondrial valine transfer RNA (mt-tRNA(Val)), which plays an integral structural role, and 52 different proteins. High relative levels in skeletal muscle and testis. Lower levels of expression in the heart, brain, placenta, lung, liver, kidney, pancreas, spleen, thymus, prostate, ovary, small intestine, colon and leukocytes. Expression is coregulated with TWNK. Belongs to the mitochondrion-specific ribosomal protein mL43 family.