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. This gene encodes a 28S subunit protein that is similar to the chicken pro-apoptotic protein p52. Transcript variants using alternative promoters or polyA sites have been mentioned in the literature but the complete description of these sequences is not available.Carim-Todd L., Cytogenet. Cell Genet. 87:85-88(1999).Wiemann S., Genome Res. 11-422-435(2001).Ota T., Nat. Genet. 36:40-45(2004).