Fig. 1: Cryo-EM structure of the active TIR–STING filament.
From: Cryo-EM structure of an active bacterial TIR–STING filament complex
a, Left, SfSTING domain organization (top) and cryo-EM density map of the active SfSTING–c-di-GMP filament complex (bottom). The colouring of the density for one dimer is used to highlight the filament organization, with TIR in pink and the STING CBD in orange. Right, an isolated SfSTING protomer (dimer) rotated 90° along the vertical axis relative to the orientation of the filament on the left. c-di-GMP is shown as a purple stick model. b, Left, a comparison of the apo (grey; top) versus the c-di-GMP-bound (orange, inside grey; bottom) SfSTING CBD highlighting the V-shaped homodimer closing in on the ligand. The apo SfSTING CBD was modelled through structural alignment with the crystal structure of a related prokaryotic TIR–STING from C. granulosa (Protein Data Bank (PDB) 6WT4)4. Right, a top-down view highlighting the closure of the β-strand ‘lid’ (90° rotated). c, A close-up view of the c-di-GMP-binding pocket of SfSTING. Several side chains make direct contacts to the c-di-GMP. Symmetry-related contacts are not shown for clarity.
