Modelling of C-terminal tail of human STING and its interaction with\rtank-binding kinase 1

Abstract

Stimulator of interferon genes (STING) plays a significant role in a cell’s intracellular defense against pathogens or selfDNA by inducing inflammation or apoptosis through a pathway known as cGAS-cGAMP-STING. STING uses one of its domains, the\rC-terminal tail (CTT) to recruit the members of the pathway. However, the structure of this domain has not been solved experimentally.\rSTING conformation is open and more flexible when inactive. When STING gets activated by cGAMP, its conformation changes to a\rclosed state covered by 4 beta-sheets over the binding site. This conformational change leads to its binding to Tank-binding kinase 1\r(TBK1). TBK1 then phosphorylates STING aiding its entry to the cell’s nucleus.\rIn this study, we focused on the loop modeling of the CTT domain in both the active and inactive STING conformations. After the\rmodeling step, the active and inactive STING structures were docked to one of the cGAS-cGAMP-STING pathway members, TBK1,\rto observe the differences of binding modes. CTT loop stayed higher in the active structure, while all the best-scored models, active or\rinactive, ended up around the same position with respect to TBK1. However, when the STING poses are compared with the cryo-EM\rimage of the complex structure, the models in the active structure chain B displayed closer results to the complex structure.