This is a conserved region of approx. 125 residues of one of the proteins that makes up the small subunit of the mitochondrial ribosome. In Saccharomyces cerevisiae the protein is MRP-S24 whereas in humans it is MRP-S28. The human mitochondrial ribosome has 29 distinct proteins in the small subunit and these have homologues in, for example, Drosophila melanogaster, Caenorhabditis elegans, and in the genomes of several fungi [1].

1: Identification of four proteins from the small subunit of the mammalian mitochondrial ribosome using a proteomics approach. Koc EC, Burkhart W, Blackburn K, Koc H, Moseley A, Spremulli LL; Protein Sci. 2001;10:471-481. PMID:11344316