Fig. 3: Cryo-EM structures of TTP alone and in complex with DSR2.

a In vitro NAD⁺ degradation assays of the full-length DSR2 protein and SIR2 ___domain-only protein in the presence or absence of TTP. The N133A/H171A catalytic mutant of the DSR2 protein was used as the negative control. 50 μM ɛ-NAD⁺ was used as the substrate. Only the WT DSR2 protein can degrade NAD⁺ in the presence of the TTP protein. The experiment was replicated three times. All experiments were replicated at least three times (mean ± SD, n = 3 independent replicates). b In vitro pull-down of wild-type (WT) DSR2 and mutants by His-tagged TTP. The gel represents three independent replicate experiments. ΔSIR2 indicates the deletion of the SIR2 subdomain (aa 304–1005), and SIR2 indicates a SIR2 ___domain-only protein (aa 1–303). The experiment was replicated three times. c Atomic model of the TTP tube (upper panel), each layer of the TTP ring is colored in wheat, gray, teal, and light blue, respectively. The lower panel shows the structure of TTP subunit in the TTP tube. The single copy of the TTP subunit is shown as cartoon representations and colored in yellow. BS1, β-sandwich ___domain 1; BS2, β-sandwich ___domain 2. d Cryo-EM structure of DSR2-TTP complex in state 1. The same color scheme as in Fig. 1a is adopted. The four TTP molecules are colored in yellow. e Cryo-EM structure of DSR2-TTP complex in state 2. The SIR2 domains are missing in this state. f Structural superposition of TTP proteins in the DSR2-TTP complex (yellow) and TTP tube (gray). A shift in the α1 helix of TTP is indicated by a blue arrow. Source data are provided as a Source data file.