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 target bacteria in a contact-dependent fashion (target cell counts decrease 1000- to 10000-fold with this CDI) (PubMed:28351921, PubMed:29923643). Uses outer membrane nucleoside transporter Tsx on target cells as a receptor (PubMed:28351921). Gains access to the cytoplasm of target cells by using integral inner membrane protein PTS system glucose-specific EIICB component (ptsG) (Probable). Targeting of the C-terminal domain (CT) domain (residues 2931-3253) in the absence of immunity protein inhibits cell growth and causes tRNA(UUC-Glu) cleavage; expression of cognate immunity protein CdiI-STECO31 neutralizes growth inhibition leaving tRNA(UUC-Glu) is intact, whereas non-cognate immunity proteins do not confer protection (PubMed:29923643). The CT domain cleaves tRNA; it is most active against tRNA(UUC-Glu), but also has modest activity against tRNA(GUC-Asp), tRNA(UUG-Gln), tRNA(CCC-Gly), tRNA(UCC-Gly), tRNA(GCC-Gly), tRNA(UUU-Lys), tRNA(GGU-Thr) and tRNA(CCA-Trp); tRNA cleavage is inhibited by cognate immunity protein CdiI. Cleavage of tRNA(UUC-Glu) occurs in the anticodon loop between cytosine(37) and 2-methyladenosine(38) (C37-m2A38) and probably also occurs in the anticodon loop of other tRNAs as well (PubMed:29923643). The CdiA protein is thought to be exported from the cell through the central lumen of CdiB, the other half of its two-partner system (TPS). The TPS domain probably remains associated with CdiB while the FHA-1 domain forms an extended filament (33 nm long) with the receptor-binding domain (RBD) at its extremity; in the secretion arrested state the C-terminus of the RBD and YP domains form a hairpin-like structure as the FHA-2, PT and CT domains are periplasmic. The YP domain is probably responsible for this arrest at the point where it re-enters the host cell periplasm. Upon binding to a target cell outer membrane receptor (Tsx for this CDI) a signal is transmitted to activate secretion. The filament becomes about 5 nm longer, the rest of CdiA is secreted and the FHA-2 domain becomes stably associated with the target cell's outer membrane where it facilitates entry of the toxic CT domain into the target cell periplasm. From there the toxic CT domain is cleaved and gains access to the target cell cytoplasm via an inner membrane protein (PTS system glucose-specific EIICB component, ptsG for this CDI). tRNase activity is metal-independent. Forms a 1:1 complex with cognate immunity protein CdiI-STECO31. Secreted to the cell surface by CdiB, its two partner secretion pathway (TPS) partner (Probable). Toxin translocation into the target cell depends on the proton motive force of the target cell, but not on tolA or tonB (By similarity). Forms filaments that extend about 33 nm away from the host cell surface; multiple filaments can be found on a single cell (PubMed:30388452). The FHA1 domain comprises the bulk of the extended filament, deletion of 100 internal residues (900-999) has a very small defect in CDI and target cell adhesion. The receptor binding domain (RBD) recognizes Tsx on target cells. The YP domain is required for stable presentation to the target cellmfac in liquid but not on solid growth media. The pFR and FHA-2 domains are critical for delivery of the CT to the target cell periplasm; deletions within these regions (1854-1954 and 2324-2423 respectively) lead to aberrant processing by target cell OmpT. FHA-2 is required for stable association with the target cell outer membrane. The PT domain is also required for CT delivery into target bacteria; it is transferred into the target cell and may be involved in autoproteolysis to release the CT domain (PubMed:30388452). The C-terminal effector domain (CT) has toxic, tRNase activity and binds to cognate immunity protein CdiI-STECO31 (PubMed:29923643). The CT domain is cleaved upon binding to receptor Tsx on target cells. In the N-terminal section; belongs to the CdiA toxin family. In the C-terminal section; belongs to the bacterial EndoU family.