CHEMBL5736653

Radioligand Binding Assay: A radioligand binding assay was developed to determine compound interactions were competitive with a tritium-labeled version of the native STING ligand, 3H-cyclic guanine (2′,5′) monophosphate adenine (3′,5′) monophosphate (3H-cGAMP). The STING constructs (WT and H232R) were comprised of residues 155-341 with both N- and C-terminal truncations; the N-terminal transmembrane domains were removed (1-154), as well as the C-terminal tail (342-379). A highly specific N-terminal biotinylation was achieved enzymatically with the E. coli biotin ligase (BirA) and inclusion of the high-affinity biotinylation peptide AviTag™. 100 nM STING protein was immobilized on 20 μg streptavidin polyvinyl toluene (SA-PVT) beads in 150 mM NaCl, 25 mM Hepes (pH 7.5), 0.1 mM EDTA, 1 mM DTT, 0.005% (v/v) Tween-20, 1% (v/v) DMSO. 100 nM 3H-cGAMP and compounds were added and allowed to come to equilibrium at room temperature (20 min). Compounds were tested in three-fold dilution series from a 100 μM starting concentration and normalized to a positive control compound that completely blocked 3H-cGAMP binding and the negative control DMSO.