Extended Data Fig. 1: Model for the regulation of mitochondrial protein lysine acylation by sirtuins.

a, Non-enzymatic protein lysine acylation occurs in the high-pH environment of mitochondria. Four or five-carbon (main chain) dicarboxyl-CoAs can form reactive anhydride intermediates and can be further captured by lysine residues. Sirtuin-mediated deacylation requires NAD⁺ as a cofactor: following formation of a complex of acylated substrate-ADP-ribose and sirtuin, a conserved histidine residue of the sirtuins deprotonates the 2′-OH of ribose that then attacks the carbonyl carbon of the alkylimidate intermediate to form a 1′,2′-cyclic intermediate, which is finally hydrolyzed to 2′/3′-O-acyl-ADP-ribose (OAADPR). b, Table summarizing the localization and in vitro deacylation activity of seven mammalian sirtuins, with their C. elegans orthologs. C. elegans has two mitochondrial sirtuins, sir-2.2 and sir-2.3; both are orthologs of mammalian SIRT4 that robustly removes five-carbon (main chain) dicarboxyl modifications.