This domain family, predicted to have RNase activity, is found in a group of toxins mainly found in Enterobacterales. It shows a conserved FGPY motif and a histidine residue and is predicted to have a mostly all-beta fold. In bacterial polymorphic toxin systems, the toxin is exported by the type 2 or type 5 secretion system [1]. Some members of this family are annotated as CdiA, a member of a contact-dependent growth inhibition system (CDI) that show diverse functions implicated in bacterial competition, including the dissipation of the proton motive force (PMF) and the degradation of DNA or RNA [2-4].

1: Polymorphic toxin systems: comprehensive characterization of trafficking modes, processing, mechanisms of action, immunity and ecology using comparative genomics. Zhang D, de Souza RF, Anantharaman V, Iyer LM, Aravind L; Biol Direct. 2012;7:18. PMID:22731697

2: Escherichia coli EC93 deploys two plasmid-encoded class I contact-dependent growth inhibition systems for antagonistic bacterial interactions. Waneskog M, Halvorsen T, Filek K, Xu F, Hammarlof DL, Hayes CS, Braaten BA, Low DA, Poole SJ, Koskiniemi S; Microb Genom. 2021; [Epub ahead of print] PMID:33646095

3: Functional and Structural Diversity of Bacterial Contact-Dependent Growth Inhibition Effectors. Cuthbert BJ, Hayes CS, Goulding CW; Front Mol Biosci. 2022;9:866854. PMID:35558562

4: A widespread family of polymorphic contact-dependent toxin delivery systems in bacteria. Aoki SK, Diner EJ, de Roodenbeke CT, Burgess BR, Poole SJ, Braaten BA, Jones AM, Webb JS, Hayes CS, Cotter PA, Low DA; Nature. 2010;468:439-442. PMID:21085179