The Effects of Phosphorylation on the Structure and Function of Motif A, an Intrinsically Disordered Region within SIRT1

characterization of these effects hampers our further understanding of the role of motif A in SIRT1 regulation. In this study, we elucidate the role phosphorylation plays in motif A's structure as well as its regulatory effects on SIRT1 activity against Ac-p65. We find that phosphomimetic mutation at Ser27 significantly increases the activation effect of motif A towards SIRT1. This result is supported by molecular dynamics simulations of the phosphomimetics, which reveal stabilization of different transient structures for motif A depending on whether Ser27 and Ser47 have been modified. A key finding suggested by this study is that phosphorylation of S27 appears to activate SIRT1 by causing motif A, which is intrinsically disordered in the WT, to fold into an ordered structure. This conclusion is based on both the experimental findings and simulation results. These findings contribute to our understanding of SIRT1 regulation, specifically the role played by phosphorylation within the N-terminal disordered region.