NCBI CDD cl00195

cl00195: SIR2 Super-family

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SIR2 superfamily of proteins includes silent information regulator 2 (Sir2) enzymes which catalyze NAD+-dependent protein/histone deacetylation, where the acetyl group from the lysine epsilon-amino group is transferred to the ADP-ribose moiety of NAD+, producing nicotinamide and the novel metabolite O-acetyl-ADP-ribose. Sir2 proteins, also known as sirtuins, are found in all eukaryotes and many archaea and prokaryotes and have been shown to regulate gene silencing, DNA repair, metabolic enzymes, and life span. The most-studied function, gene silencing, involves the inactivation of chromosome domains containing key regulatory genes by packaging them into a specialized chromatin structure that is inaccessible to DNA-binding proteins. The oligomerization state of Sir2 appears to be organism-dependent, sometimes occurring as a monomer and sometimes as a multimer. Also included in this superfamily is a group of uncharacterized Sir2-like proteins which lack certain key catalytic residues and conserved zinc binding cysteines.