Minimal version of the CRISPR polymerase domain. Predicted to generate cyclic nucleotides, potentially sensed by CARF domains which in turn activate various effector domain including HEPN RNases, CARF sensor and effectors are found in conserved genome contexts. Part of a broader class of conflict systems reliant on the production of second messenger nucleotide or nucleotide derivatives. Implicates CRISPR polymerase of the Type III CRISPR/Cas systems in a nucleotide synthetase functional role [1].

1: Comparative genomic analyses reveal a vast, novel network of nucleotide-centric systems in biological conflicts, immunity and signaling. Burroughs AM, Zhang D, Schaffer DE, Iyer LM, Aravind L; Nucleic Acids Res. 2015;43:10633-10654. PMID:26590262