Fig. 4: TIR-mediated NAD+ cleavage is driven by STING oligomerization.
From: Cryo-EM structure of an active bacterial TIR–STING filament complex
a, A bar-graph representation of NADase activity measured with the NAD+ fluorescent analogue nicotinamide 1,N6-ethenoadenine dinucleotide for a panel of SfSTING residue substitutions at a range of enzyme concentrations. NADase activity is measured as fluorescence intensity (relative fluorescence units (RFU)) at about 5 min. Each bar within a set corresponds to 0.1, 1 or 10 μM enzyme. The baseline threshold indicates the background fluorescent signal. The error bars indicate the standard deviation for the average of three biological replicates each with three technical replicates. *P < 0.0001 (one-way analysis of variance comparing the mean value for each mutant to that of the wild type (WT) at the same protein concentration); P values for bars without an asterisk are greater than 0.05 and considered not significantly different. b, Negative-stain micrograph images for select SfSTING mutants and the wild type in the presence of c-di-GMP. Scale bars, 100 nm. Each image is representative of n = 6 micrograph images. c, Cell growth curves for E. coli cultures expressing a select panel of SfSTING mutants and the wild type. The data are representative of more than three independent biological replicates each with three technical replicates. The mean curve is shown for one biological replicate. d, A schematic model describing the process of SfSTING NADase activation through ligand binding and filament formation. CD-NTase, cGAS/DncV-like nucleotidyltransferase.
