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.

The 28S subunit of the mammalian mitoribosome may play a crucial and characteristic role in translation initiation.

This gene encodes a 28S subunit protein that is one of the more highly conserved mitochondrial ribosomal proteins among mammals, Drosophila and Caenorhabditis elegans.