cGAS (Cyclic GMP-AMP synthase) is a nucleotidyltransferase that catalyzes the formation of cyclic GMP-AMP (cGAMP) from ATP and GTP and plays a key role in innate immunity. Catalysis involves both the formation of 2', 5' phosphodiester linkage at the GpA step and the formation of 3', 5' phosphodiester linkage at the ApG step. This produces c[G(2',5')pA(3'5')p] responses. cGAS also binds cytosolic DNA directly, leading to the activation and synthesis of cGAMP. Then, a second messenger binds to and activates TMEM173/STING thereby triggering type-I interferon production. cGAS is also involved in innate immune sensorship of infection, detection of DNA from bacteria, response to cellular stress, DNA damage, and regulation of cellular senescence.
2'3'-cGAMP synthase; cf150; cGAMP synthase; Cyclic GMP-AMP synthase; Mab-21 domain-containing protein 1; protein MB21D1