Custom Anti-cGAS Antibody Enables E2-CBASS Anti-Phage Immunity Discovery

Project Snapshot — A Nature Microbiology study revealed that the E2 enzyme in E2-CBASS regulates cGAS via ubiquitination mimicry, promoting poly-cGAS formation and cGAMP production to confer anti-phage immunity in Serratia marcescens. AtaGenix provided a custom rabbit anti-cGAS polyclonal antibody that reliably distinguished cGAS monomers (46 kDa), cGAS-E2 complexes (64 kDa), and poly-cGAS (>100 kDa) in Western blot — enabling the study’s core mechanistic validation.

Fig. 1. Cryo-EM structure of the cGAS-E2 complex. E2 binds the cGAS C-terminal region via transient thioester (C101) and stable isopeptide (K159) bonds. Adapted from Nat Microbiol 2024.

Covalent Complex Formation: Cryo-EM confirmed E2 binds the cGAS C-terminal region. Critical residues (cGAS G406, E2 C101/K159) mediate two reversible covalent bonds: a transient thioester (cGAS Y405–E2 C101) and a stable isopeptide (cGAS Y405–E2 K159), regulated by pH.

Dual Enzymatic Activity: E2 exhibits both cysteine protease and ubiquitin ligase-like activity — cleaving the cGAS C-terminal G406-E407 peptide (>80% efficiency) and promoting poly-cGAS formation via inter-molecular isopeptide bonds.

Signal Amplification: Poly-cGAS is the active form, enhancing 3′,2′-cGAMP synthesis by 2.3-fold. cGAMP activates the 2TM-SAVED effector protein, triggering membrane disruption and abortive infection to block phage replication.

Fig. 2. Western blot detection of cGAS and its complexes using AtaGenix custom anti-cGAS pAb. Monomers (46 kDa), cGAS-E2 complexes (64 kDa), and poly-cGAS (>100 kDa) clearly resolved. Adapted from Nat Microbiol 2024.

Why This Matters

This study identifies the E2 enzyme as a multifunctional regulator (protease/E2/E3) in E2-CBASS, filling key gaps in understanding how prokaryotic anti-phage immunity operates at a molecular level. The discovery of ubiquitination mimicry in bacteria reveals unexpected evolutionary links between prokaryotic and eukaryotic innate immunity. The AtaGenix custom anti-cGAS polyclonal antibody was the essential detection tool — no commercial antibody could resolve cGAS monomers, complexes, and poly-cGAS simultaneously in Western blot, making this a de novo custom development critical to the study’s conclusions.

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