16S rRNA endonuclease CdiA

UniProtKB accession:  D5CBA0

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UniProtKB description:  Toxic component of a toxin-immunity protein module, which functions as a cellular contact-dependent growth inhibition (CDI) system. CDI modules allow bacteria to communicate with and inhibit the growth of closely related neighboring bacteria in a contact-dependent fashion; upon forced induction decreases E.cloacae target cell counts about 20-fold, about 100-fold in E.coli. Intracellular expression of CdiA-CT (residues 3087-3321) inhibits E.coli cell growth when induced, but coexpression with its cognate immunity protein CdiI allows cell growth. Cleaves 16S rRNA in vivo and in vitro between adenine 1493 and guanosine 1494 of E.coli 16S rRNA. Inhibition of 16S rRNA cleavage is specific to the cognate immunity protein, non-cognate CdiI from E.chrysanthemi strain EC16 does not inhibit this protein (PubMed:24657090). Purified CdiA-CT inhibits E.coli cell growth when added to cultures but not when added as a complex with cognate CdiI, suggesting cognate CdiI prevents import into the target cell. CdiA-CT (without CdiI) is probably imported in an F-pilus-mediated fashion, although it is not clear if this is physiologically significant (PubMed:24889811). Gains access to the cytoplasm of target cells by using integral inner membrane protein FtsH (PubMed:26305955).