Plays an important role in assembly of the mitochondrial large ribosomal subunit (PubMed:25683715). As a component of a functional protein-RNA module, consisting of RCC1L, NGRN, RPUSD3, RPUSD4, TRUB2, FASTKD2 and 16S mitochondrial ribosomal RNA (16S mt-rRNA), controls 16S mt-rRNA abundance and is required for intra-mitochondrial translation (PubMed:27667664, PubMed:25683715, PubMed:26370583). May play a role in mitochondrial apoptosis. Monomer. Found in a complex with GRSF1, DDX28, DHX30 and FASTKD5. Associates with the 16S mitochondrial rRNA (16S mt-rRNA) (PubMed:25683715). Forms a regulatory protein-RNA complex, consisting of RCC1L, NGRN, RPUSD3, RPUSD4, TRUB2, FASTKD2 and 16S mt-rRNA (PubMed:27667664). Localizes to mitochondrial RNA granules found in close proximity to the mitochondrial nucleoids. Expression detected in spleen, thymus, testis, ovary, colon, heart, smooth muscle, kidney, brain, lung, liver and white adipose tissue with highest expression in heart, smooth muscle and thyroid. The disease is caused by variants affecting the gene represented in this entry. Belongs to the FAST kinase family. It is uncertain whether Met-1 or Met-17 is the initiator. Extended N-terminus. Extended N-terminus.