Mitochondrial Ribosomal Protein S9 (MRPS9)

Mitochondrial ribosomes (mitoribosomes) consist of a small 28S subunit and a large 39S subunit. They have an estimated 75% protein to rRNA composition compared to prokaryotic ribosomes, where this ratio is reversed. Another difference between mammalian mitoribosomes and prokaryotic ribosomes is that the latter contain a 5S rRNA. Among different species, the proteins comprising the mitoribosome differ greatly in sequence, and sometimes in biochemical properties, which prevents easy recognition by sequence homology.

MRPS9 encodes a 28S subunit protein. The deduced 387-amino acid protein has a calculated molecular mass of 44.8 kD. Removal of a predicted 51-amino acid N-terminal mitochondrial localization signal results in a mature 38.8-kD protein.