Extended Data Fig. 4: Comparison of cyclic dinucleotide-bound states of SfSTING.
From: Cryo-EM structure of an active bacterial TIR–STING filament complex
a, c-di-GMP bound SfSTING superposition and comparison with apo C. granulosa CgSTING (PDB 6WT5)4. b, 3′,3′-cGAMP bound SfSTING CBD presents an intermediately compact state between the predicted apo (model prepared by superposing an SfSTING monomer with apo CgSTING PDB 6WT4 as guide) and the c-di-GMP bound structure (left, middle). Density is insufficient to accurately model the complete β-lid for the 3′,3′-cGAMP state. Panel at right presents a side view of a monomer of SfSTING and showcases the dynamic rotation/translation of each monomer relative to one another that sequesters the cyclic dinucleotide within the binding pocket. Orange arrows plot the domain rotation from apo (model, grey) to c-di-GMP bound state (using Modevectors python script). Movement of one monomer shown for clarity. c, Comparison of 3′,3′-cGAMP with SfSTING to 3′,3′-cGAMP with Flavobacteriaceae sp. FsSTING (PDB 6WT4)4. Superposition RMSD of 2 Å with a sequence identity in the STING CBD of only 25% highlights the incredible degree of structural conservation in this family of bacterial proteins and exemplifies the shared mechanism for cyclic dinucleotide recognition. d, Conservation of bacterial STING sequence plotted on the SfSTING monomeric STING CBD domain. Conservation based on multiple sequence alignment of 102 bacterial STING CBD sequences. Analysis and colouring done using the ConSurf webserver36. Conservation scores range from 1 to 9 with increasing conservation. Highest conservation is evident within the core CDN binding pocket and along the dimerization interface. Weak conservation is found on the surface and at predicted filament contact sites. e, SfSTING structural comparison with the apo structure of a TIR-STING homolog from Crassostrea gigas (PDB 6WT6) and cryo-EM structures of human (PDB 6NT5) and chicken (PDB 6NT8) STING in the apo and 2′,3′-cGAMP-bound states highlights differences in linker crossover and domain packing. Portions of STING CBD structures omitted for clarity.
