SIRT1 Top 40 Hits: Use of One-Bead, One-Compound Acetyl-Peptide Libraries and Quantum Dots to Probe Deacetylase Specificity

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Abstract
A novel, high-throughput method for determining deacetylase substrate specificity was developed using a one-bead, one-compound (OBOC) acetyl-peptide library with a quantum dot tagging strategy and automated bead-sorting. A 5-mer OBOC peptide library of 104 907 unique sequences was constructed around a central ε-amino acetylated lysine. The library was screened using the human NAD+-dependent deacetylase SIRT1 for the most efficiently deacetylated peptide sequences. Beads preferentially deacetylated by SIRT1 were biotinylated and labeled with streptavidin-coated quantum dots. After fluorescent bead-sorting, the top 39 brightest beads were sequenced by mass spectrometry. In-solution deacetylase assays on randomly chosen hit and nonhit sequences revealed that hits correlated with increased catalytic activity by as much as 20-fold. We found that SIRT1 can discriminate peptide substrates in a context-dependent fashion.