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. Author manuscript; available in PMC: 2021 Mar 2.
Published in final edited form as: Nature. 2020 Sep 2;586(7829):429–433. doi: 10.1038/s41586-020-2719-5

Figure 1 |. Structure of bacterial STING and definition of metazoan-specific insertions.

Figure 1 |

a, Crystal structure of a STING receptor from the bacterium Flavobacteriaceae sp. (orange) in complex with the cyclic dinucleotide 3′,3′-cGAMP. The FsSTING–3′,3′-cGAMP structure demonstrates a conserved mechanism of cyclic dinucleotide sensing shared between bacteria and human cells, and allows direct comparison with the human STING–2′,3′-cGAMP complex (PDB 4KSY, blue). For clarity, one monomer of each homodimer is depicted in grey.

b, STING topology diagrams denoting α-helices (rectangles), β-strands (arrows), and residues important for ligand recognition (FsSTING F92, D169, R153; hSTING Y167, E260, R232 in red, R238). Bacterial STING receptors reveal a minimal protein architecture required for cyclic dinucleotide sensing and allow direct definition of the structural insertions (red) in metazoan STING sequences required for signaling in animal cells.