6ct9
From Proteopedia
Structure of the human cGAS-DNA complex
Structural highlights
Function[CGAS_HUMAN] Nucleotidyltransferase that catalyzes formation of cyclic GMP-AMP (cGAMP) from ATP and GTP and exhibits antiviral activity. Has antiviral activity by acting as a key cytosolic DNA sensor, the presence of DNA in the cytoplasm being a danger signal that triggers the immune responses. Binds cytosolic DNA directly, leading to activation and synthesis of cGAMP, a second messenger that binds to and activates TMEM173/STING, thereby triggering type-I interferon production.[1] [2] Publication Abstract from PubMedCyclic GMP-AMP synthase (cGAS) recognition of cytosolic DNA is critical for immune responses to pathogen replication, cellular stress, and cancer. Existing structures of the mouse cGAS-DNA complex provide a model for enzyme activation but do not explain why human cGAS exhibits severely reduced levels of cyclic GMP-AMP (cGAMP) synthesis compared to other mammals. Here, we discover that enhanced DNA-length specificity restrains human cGAS activation. Using reconstitution of cGAMP signaling in bacteria, we mapped the determinant of human cGAS regulation to two amino acid substitutions in the DNA-binding surface. Human-specific substitutions are necessary and sufficient to direct preferential detection of long DNA. Crystal structures reveal why removal of human substitutions relaxes DNA-length specificity and explain how human-specific DNA interactions favor cGAS oligomerization. These results define how DNA-sensing in humans adapted for enhanced specificity and provide a model of the active human cGAS-DNA complex to enable structure-guided design of cGAS therapeutics. Structure of the Human cGAS-DNA Complex Reveals Enhanced Control of Immune Surveillance.,Zhou W, Whiteley AT, de Oliveira Mann CC, Morehouse BR, Nowak RP, Fischer ES, Gray NS, Mekalanos JJ, Kranzusch PJ Cell. 2018 Jul 12;174(2):300-311.e11. doi: 10.1016/j.cell.2018.06.026. PMID:30007416[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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