Mammalian mitochondrial ribosomal proteins are encoded by nuclear genes and help in protein synthesis within the;mitochondrion. 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. 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 C.;elegans. Splice variants that differ in the 5 UTR have been found for this gene; all variants encode the same;protein. Pseudogenes corresponding to this gene are found on chromosomes 1q, 4p, 4q, and 20q.