Regulator of mitochondrial ribosome biogenesis and translation. Binds to mitochondrial ribosomal RNAs 16S, 12S and 7S (By similarity). Targets NSUN4 RNA methyltransferase to the mitochondrial large ribosomal subunit. Heterodimer with NSUN4; this interaction may be required for NSUN4 recruitment to the mitochondrial large ribosomal subunit. Widely expressed, with highest levels in liver, followed by testis, kidney and brain. The MTERF repeats form a half-donut shaped, right-handed superhelix, where the concave side displays a positively charged path for nucleic acid interaction. Ablation of the gene is not viable. At 8.5 dpc, mutant homozygous embryos exhibit much reduced size, lack of heart and no optic disks. Conditional knockout in heart leads to severe mitochondrial cardiomyopathy. Premature death occurs at about 21 weeks and decreased body weight is observed from 15 weeks until death. Belongs to the mTERF family. Truncated N-terminus. Truncated N-terminus.