Many bacteria pathogens transport virulence proteins, termed effector proteins, into host cells via specialized protein secretion systems such as type III secretion systems (T3SS). Enteropathogenic Escherichia coli (EPEC) can block NF-κB activation via a T3SS-dependent mechanism and recent research has shown that the effector protein NleE is necessary and sufficient to block NF-κB activation. NleE acts through inactivating the ubiquitin-chain binding activity of the host proteins TAB2 and TAB3 by modifying their NZF domains. TAB2 and TAB3 are homologous proteins with redundant functions that bind to TAK1 and are therefore involved in NF-κB signalling pathway. OspZ, a close homologue of NleE from Shigella sp. also has the ability to block translocation of the p65 subunit of the NF-κB transcription factor complex into the host cell nucleus. Here, we found OspZ decreased cxcl2 gene transcription level in Shigella infected mouse macrophages. Using the Yeast Two Hybrid System we showed that full length of NleE and OspZ bind with TAB3 in yeast and established that the N-terminal 53 amino acids of NleE and the CUE domain of TAB3 are critical for their interaction. NleE missing the N-terminal 53 amino acid had no inhibitory effect on NF-κB-mediated luciferase activity. The data presented here suggests that the sites of NleE and OspZ required for binding to TAB3 are different from the catalytic sites and that they are essential for the function of NleE/OspZ in the inhibition of the host immune response.