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 (T4, T5 and T6) 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_024167427.1. Belongs to the peptidase M67B family.