Effects of resveratrol and piceatannol on the FdL-peptide deacetylation activities of Sirt3 and Sirt5.

<p><b>A</b> Deacetylation activity of Sirt3 against FdL2 (○) and Sirt5 against FdL1 (•) determined at increasing resveratrol concentrations. Activities are given relative to the value in absence of resveratrol. <b>B</b> Dose-response experiment for the piceatannol-dependent stimulation of FdL1 deacetylation by Sirt5. <b>C</b> Inhibition of Sirt3 FDL2 deacetylation activity by piceatannol. Error bars represent standard deviations.</p

Model for Sirtuin regulation by resveratrol-like compounds.

<p><b>A</b> Superimposition of Sirt5/FdL1/resveratrol and Sirt5/succinylated H3 peptide/NAD⁺. The movement of the β8/α13 loop is indicated by an arrow. The succinylated H3 peptide and the NAD⁺ molecule are omitted for clarity. <b>B</b> Model for the regulation of Sirtuins by resveratrol-like compounds. After binding of the substrate polypeptide the small molecule attaches to a “docking patch” (DP). It induces ordering of an “adaptable loop” (AL), leading to closure of the peptide exit and stabilization of the enzyme/substrate complex. Depending on the fit between substrate and small-molecule, the substrate is properly oriented in the active site (AS; e.g. Sirt5/Cytochrome c/resveratrol) or adopts a non-productive conformation (e.g. Sirt3/GDH/resveratrol), leading to stimulation or inhibition of turnover, respectively. After deacetylation, the activator dissociates, opening the peptide exit for product release.</p

Crystal structure of human Sirt5 in complex with FdL1-peptide and resveratrol.

<p><b>A</b> Overall structure of the Sirt5/FdL1/resveratrol complex. Secondary structure elements are labeled as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049761#pone.0049761-Schuetz1" target="_blank">[42]</a> (elements not present here are in parentheses). <b>B</b> Closer view of the activator binding site, showing the direct interaction between substrate peptide and resveratrol. The 2F_O–F_C electron density is contoured at 1σ. <b>C</b> Surface representation of the Sirt5 ligand binding sites, showing that the activator closes the peptide channel entrance. The peptide is shown as sticks, the activator as calotte model in orange. <b>D</b> Piceatannol dose response experiments showing the changes in stimulated Sirt5 FdL1 deacetylation activity upon mutation of residues in the resveratrol binding loops. The assignment of symbols to Sirt5 residue replacement mutations, deletions (Δ), or a single residue insertion (R71-P-G72: Pro insertion) is indicated on the right side.</p

Effects of resveratrol and piceatannol on Sirt3 and Sirt5 deacetylation activities against fluorophore-free peptides and proteins.

<p><b>A</b> Overlay of the Sirt5/FdL1/resveratrol (FdL1 in green, activator omitted for clarity) and Sirt5/succinylated H3 peptide/NAD⁺ (H3 peptide in atom type coloring, NAD⁺ omitted for clarity) complexes. The fluorophore occupies the site normally accommodating residues of the substrate polypeptide. <b>B</b> Overlay of Sirt5/FdL1/resveratrol (FdL1 omitted for clarity) and Sirt5/succinylated H3-peptide/NAD⁺ complex. Ligands are colored according to atom types with carbon atoms in green (resveratrol), yellow (H3 peptide), and blue (NAD⁺). <b>C+D</b> Sirt5-dependent deacetylation of Prx1-Lys197 peptide (<b>C</b>) and Prx1 protein specifically acetylated at Lys197 (<b>D</b>) is activated by resveratrol-related compounds. <b>E</b> Sirt5-dependent deacetylation of Cytochrome c determined in an ELISA shows that resveratrol and piceatannol stimulate this activity (which leads to a loss of signal in this assay). <b>F</b> Dose-reponse experiment for the piceatannol-dependent stimulation of Cytochrome c deacetyalation by Sirt5. Shown is the loss in absorption at different piceatannol concentrations relative to untreated Cytochrome c. <b>G</b> Sirt3-dependent GDH deacetylation tested in an ELISA (deacetylation decreases absorbance) shows an inhibitory effect of resveratrol. Error bars represent standard errors of linear fits to time-series experiments (C+D) or standard deviations (E–G), respectively.</p

Crystal structure of human Sirt3 in complex with FdL1-peptide and piceatannol.

<p><b>A</b> Overall structure of the Sirt3/FdL1/piceatannol complex. Secondary structure elements are labeled according to the Sirt5/FdL1/resveratrol complex for comparison. <b>B</b> Closer view of the activator binding site, showing the direct interaction between substrate peptide and piceatannol similar to the arrangement in the Sirt5/FdL1/resveratrol complex structure. The 2F_O-F_C electron density is contoured at 1σ. Residues of the symmetry related Sirt3 monomer (*) contributing to piceatannol binding are shown in yellow. <b>C</b> Interface between Sirt3 (blue) and its symmetry related monomer (orange) showing the binding mode for the FdL1-peptide and piceatannol. Ligands and residues involved in their binding are presented as blue and yellow sticks. <b>D</b> Superimposition of Sirt5/FdL1/resveratrol (blue) and Sirt3/FdL1/piceatannol (yellow). The residues N-terminal to the acetylated lysine are labeled for comparison.</p

Dependency of the resveratrol/piceatannol effects on the substrate sequence and the type of acyl modification.

<p><b>A</b> Sirt5-dependent deacetylation of p53-Lys382 peptide is not affected by resveratrol. <b>B+C</b> In contrast to its stimulated deacetylation activity, Sirt5’s deacylation activity against succinylated FdL1 (<b>B</b>) and Prx1-Lys197 (<b>C</b>) peptides is inhibited by resveratrol and piceatannol. Error bars represent standard errors of linear fits to time-series experiments.</p