SIRT3
Description
The SIRT3 (sirtuin 3) is a protein-coding gene located on chromosome 11.
NAD-dependent deacetylase sirtuin-3, mitochondrial also known as SIRT3 is a protein that in humans is encoded by the SIRT3 gene [sirtuin (silent mating type information regulation 2 homolog) 3 (S. cerevisiae)]. SIRT3 is member of the mammalian sirtuin family of proteins, which are homologs to the yeast Sir2 protein. SIRT3 exhibits NAD+-dependent deacetylase activity. Members of the sirtuin family are characterized by a sirtuin core domain and grouped into four classes, and the protein encoded by this gene is included in class I of the sirtuin family. The human sirtuins have a range of molecular functions and have emerged as important proteins in aging, stress resistance, and metabolic regulation. Yeast sirtuin proteins are known to regulate epigenetic gene silencing and suppress recombination of rDNA. In addition to protein deacetylation, studies have shown that the human sirtuins may also function as intracellular regulatory proteins with mono ADP ribosyltransferase activity.
== Structure == SIRT3 is a soluble protein located in the mitochondrial matrix, and contains a mitochondrial processing peptide at the N-terminus. A set of crystal structures of human SIRT3 have been solved, including an apo-structure with no substrate, a structure with a peptide containing acetyl lysine of its natural substrate acetyl-CoA synthetase 2, a reaction intermediate structure trapped by a thioacetyl peptide, and a structure with the dethioacetylated peptide bond. These structures show the conformational changes induced by the two substrates required for the reaction, the acetylated substrate peptide and NAD+. In addition, a binding study by isothermal titration calorimetry suggests that the acetylated peptide is the first substrate to bind to SIRT3, prior to NAD+.
NAD-dependent protein deacetylase (PubMed:12186850, PubMed:12374852, PubMed:16788062, PubMed:18680753, PubMed:18794531, PubMed:23283301, PubMed:24121500, PubMed:24252090, PubMed:19535340). Activates or deactivates mitochondrial target proteins by deacetylating key lysine residues (PubMed:12186850, PubMed:12374852, PubMed:16788062, PubMed:18680753, PubMed:18794531, PubMed:23283301, PubMed:24121500, PubMed:24252090). Known targets include ACSS1, IDH, GDH, SOD2, PDHA1, LCAD, SDHA and the ATP synthase subunit ATP5PO (PubMed:16788062, PubMed:18680753, PubMed:24121500, PubMed:24252090, PubMed:19535340). Contributes to the regulation of the cellular energy metabolism (PubMed:24252090). Important for regulating tissue-specific ATP levels (PubMed:18794531). In response to metabolic stress, deacetylates transcription factor FOXO3 and recruits FOXO3 and mitochondrial RNA polymerase POLRMT to mtDNA to promote mtDNA transcription (PubMed:23283301). Acts as a regulator of ceramide metabolism by mediating deacetylation of ceramide synthases CERS1, CERS2 and CERS6, thereby increasing their activity and promoting mitochondrial ceramide accumulation (By similarity). Regulates hepatic lipogenesis. Uses NAD(+) substrate imported by SLC25A47, triggering downstream activation of PRKAA1/AMPK-alpha signaling cascade that ultimately downregulates sterol regulatory element-binding protein (SREBP) transcriptional activities and ATP-consuming lipogenesis to restore cellular energy balance. {ECO:0000250|UniProtKB:Q8R104, ECO:0000269|PubMed:12186850, ECO:0000269|PubMed:12374852, ECO:0000269|PubMed:16788062, ECO:0000269|PubMed:18680753, ECO:0000269|PubMed:18794531, ECO:0000269|PubMed:19535340, ECO:0000269|PubMed:23283301, ECO:0000269|PubMed:24121500, ECO:0000269|PubMed:24252090}
SIRT3 is also known as SIR2L3.
