CBASS (cyclic oligonucleotide-based antiphage signaling system) provides immunity against bacteriophage. The CD-NTase protein synthesizes cyclic nucleotides in response to infection; these serve as specific second messenger signals. The signals activate a diverse range of effectors, leading to bacterial cell death and thus abortive phage infection. A type I-D(GG) CBASS system (PubMed:32839535). Binds cyclic dinucleotides: binds c-di-GMP (synthesized by the cognate CdnE encoded upstream in the same operon), cyclic 3'3'-cyclic GMP-AMP (3'3'-cGAMP) but not cUMP-AMP (PubMed:32877915). The effector protein for this CBASS system, its activity is stimulated by c-di-GMP and leads to cell death (Probable). Homodimer. The cyclic nucleotide binds in the C-terminal bacterial STING region (PubMed:32877915). Comparison of structures from 2 different bacteria suggests that cyclic nucleotide binding causes domain rotation, which forms a lid and seals the nucleotide-binding pocket (Probable). In the C-terminal section; belongs to the bacterial STING family.