About MRPL / Mitochondrial Ribosomal Protein:
The mitochondrial ribosome, also known as the mitoribosome, is a protein complex that functions as a riboprotein for translating mitochondrial mRNAs encoded in mtDNA. Mito Ribosomes have two subunits, similar to cytoplasmic ribosomes: large (mtLSU) and small (mtSSU) (mt-SSU). The rRNA/protein ratio in cytoplasmic ribosomes, on the other hand, is different. Mitoribosomes have fewer rRNAs and contain a variety of specialized proteins.
Mitochondria in yeast contain approximately 1000 proteins and 1500 proteins in humans. In yeast and humans, however, mitochondrial DNA encodes only 8 and 13 proteins, respectively. Cytoplasmic ribosomes produce the majority of mitochondrial proteins. In mitochondria, proteins that are essential components of the electron transport chain are translated.
Mitochondrial Ribosomal Protein Structure
Mammalian mitoribosomes are composed of small 28S and large 39S subunits that combine to form a 55S mitoribosome. Plant mitoribosomes are made up of small 33S and large 50S subunits that combine to form a 78S mitoribosome.
Animal mitoribosomes have only two rRNAs, 12S (SSU) and 16S (LSU), which are greatly reduced in size compared to their larger homologs. Except for animals, fungi, alveolates, and euglenozoans, most eukaryotes use 5S mitoribosome RNA. Animals have co-opted an Mt-tRNA (Val invertebrates) to fill the gap left by a missing 5S.