A protein dimer containing two STING monomers. It binds cyclic purine di-nucleotides. Activation of the sting complex by 2',5'-3'-5'-cyclic GMP-AMP activates nuclear transcription factor kB (NF-kB) and interferon regulatory factor 3 (IRF3) which then induce transcription of the genes encoding type I IFN and cytokines active in the innate immune response. [ http://www.ncbi.nlm.nih.gov/pubmed/22705373 http://www.ncbi.nlm.nih.gov/pubmed/23706668 http://www.ncbi.nlm.nih.gov/pubmed/23910378 ]