SIR2 family 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.
Comment:The acetylated Lys side chain has an extended conformation. H118, V163, F165, L169, and V196 side chains form van der Waals interactions with the aliphatic atoms of the Lys side chain. The acetyl methyl group is in van der Waals contact with I102 and H118.
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