Genes encoding PPR (pentatricopeptide repeat)-containing proteins constitute one of the largest gene families in plants. The majority of these proteins are predicted to target organelles and to bind to RNA. Strikingly, there is a dearth of these proteins in mammals, although genomic searches reveal six candidates, all of which are also predicted to target the mitochondrion. One of these proteins, MRPS27is participated in transcription and translation respectively. [PMID:18939947] MRPS27is a component of the small subunit of the mitochondrial ribosome that is encoded by the nuclear genome [PMID: 11279123].