Members of this family are predicted to function as toxins in bacterial polymorphic toxin systems, including DddA from Burkholderia cenocepacia [1]. DddA is part of the cellular contact- dependent growth inhibition (CDI) system that allows bacteria to communicate with and inhibit the growth of closely related neighbouring bacteria in a contact-dependent fashion. Its deaminase domain has double-stranded DNA cytidine deaminase activity and can be used for CRISPR-free mitochondrial base editing [2].

1: Evolution of the deaminase fold and multiple origins of eukaryotic editing and mutagenic nucleic acid deaminases from bacterial toxin systems. Iyer LM, Zhang D, Rogozin IB, Aravind L; Nucleic Acids Res. 2011; [Epub ahead of print] PMID:21890906

2: A bacterial cytidine deaminase toxin enables CRISPR-free mitochondrial base editing. Mok BY, de Moraes MH, Zeng J, Bosch DE, Kotrys AV, Raguram A, Hsu F, Radey MC, Peterson SB, Mootha VK, Mougous JD, Liu DR; Nature. 2020;583:631-637. PMID:32641830