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Publication Abstract from PubMed

cGAS activates innate immune responses against cytosolic double-stranded DNA. Here, by determining crystal structures of cGAS at various reaction stages, we report a unifying catalytic mechanism. apo-cGAS assumes an array of inactive conformations and binds NTPs nonproductively. Dimerization-coupled double-stranded DNA-binding then affixes the active site into a rigid lock for productive metal*substrate binding. A web-like network of protein*NTP, intra-NTP, and inter-NTP interactions ensures the stepwise synthesis of 2'-5'/3'-5'-linked cGAMP while discriminating against noncognate NTPs and off-pathway intermediates. One divalent metal is sufficient for productive substrate binding, and capturing the second divalent metal is tightly coupled to nucleotide and linkage specificities, a process which manganese is preferred over magnesium by 100-fold. Additionally, we elucidate how mouse cGAS achieves more stringent NTP and linkage specificities than human cGAS. Together, our results reveal that an adaptable, yet precise lock-and-key-like mechanism underpins cGAS catalysis.

The structural basis for 2'-5'/3'-5'-cGAMP synthesis by cGAS.,Wu S, Gabelli SB, Sohn J Nat Commun. 2024 May 13;15(1):4012. doi: 10.1038/s41467-024-48365-3. PMID:38740774^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.