Shigella flexneri, a Gram-negative bacterium that damages th...

created [InstanceEdit:9956599] Shamovsky, Veronica, 2025-06-13
dbId 9956650
displayName Shigella flexneri, a Gram-negative bacterium that damages th...
literatureReference
modified [InstanceEdit:9963558] Shamovsky, Veronica, 2025-08-14
schemaClass Summation
text Shigella flexneri, a Gram-negative bacterium that damages the colonic epithelium and causes bacillary dysentery in humans, secretes the type III secretion system effector OspC3. OspC3 inactivates caspase-4 (CASP4) and suppresses CASP4-mediated pyroptosis, a lytic form of cell death triggered by intracellular lipopolysaccharide (LPS) (Kobayashi T. et al., 2013; Li Z. et al., 2021; Hou Y. et al., 2023). OspC3 catalyzes ADP-riboxanation of CASP4 by transferring ADP-ribose from NAD? to the N? atom of an arginine residue (R314 in CASP4), followed by deamination of an N? group to form an oxazolidine ring structure (Hou Y. et al., 2023). The catalytic activity of OspC3 is stimulated by its interaction with calcium-free calmodulin (CALM), which reconfigures the OspC3 catalytic pocket to facilitate NAD? binding and promote stable ternary complex formation with CASP4 (Li Z. et al., 2021; Hou Y. et al., 2023). A homologous effector, CopC from Chromobacterium violaceum, shares ADP-riboxanase activity but differs in substrate specificity, targeting apoptotic caspases such as CASP3, CASP7, CASP8, and CASP9. Like OspC3, CopC also binds CALM to become catalytically active (Liu Y. et al., 2022; Zhang K. et al., 2022).
Cite Us!