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inhibitor (or immunity protein) of the contact-dependent growth inhibition (CDI) system of Yersinia kristensenii, and similar proteins CDI toxins are expressed by gram-negative bacteria as part of a mechanism to inhibit the growth of neighboring cells. This model represents the inhibitor (CdiI, also called CdiI immunity protein) of the CdiA effector protein from Yersinia kristensenii (which is an RNase), and similar proteins. CdiA secretion is dependent on the outer membrane protein CdiB. Upon binding to a receptor on the surface of target bacteria, the CDI toxin is delivered via its C-terminal domain (CdiA-CT). The CdiI immunity proteins are intracellular proteins that inactivate the toxin/effector protein. They are specific for their cognate CdiA-CT and do not protect cells from the toxins of other CDI+ bacteria. The CdiI immunity protein binds the CdiA toxin via its C-terminal domain to prevent auto-inhibition. Thus, CDI systems encode a complex network of toxin-immunity protein pairs that are deployed for intercellular competition. Y. kristensenii CdiI binds directly over the putative active site of the CdiA-CT toxin and likely neutralizes toxicity by blocking access to RNA substrates. |
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Jiyao W et al.(2023). "The conserved domain database in 2023.",