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 II-A(GA) CBASS system (PubMed:32839535). Protects E.coli against phage infection. When capV and dncV are introduced in E.coli MG1655 there is 1000-fold protection against phage P1; protection against other phage (T2, T4, T5, T6 and lambda-vir) requires the 2 subsequent genes. Part of the CBASS operon consisting of capV-dncV-cap2-cap3. The sequence of this protein is available under the NCBI RefSeq accession WP_000390951.1. In the C-terminal section; belongs to the HesA/MoeB/ThiF family.