This region is characteristic of Silent information regulator 2 (Sir2) proteins, or sirtuins. These are protein deacetylases that depend on nicotine adenine dinucleotide (NAD). They are found in many subcellular locations, including the nucleus, cytoplasm and mitochondria. Eukaryotic forms play in important role in the regulation of transcriptional repression. Moreover, they are involved in microtubule organisation and DNA damage repair processes [1].i

1: Sirtuins: Sir2-related NAD-dependent protein deacetylases. North BJ, Verdin E; Genome Biol 2004;5:224. PMID:15128440