Fig. 4.

T9SS effector processing by the PorQUZ attachment complex. The T9SS effector is conveyed by the PorV shuttle to the PorQUZ complex. The PorU proteolytic domain cleaves the CTD, forming a thioester-bound complex between PorU and the processed substrate. The CTD is then either released in the medium or attached to the A-LPS after the nucleophilic attack of the free amino groups of primary amines, amino acids, short peptides or A-LPS. The A-LPS is synthesized by the Wba/Vim pathway and transported to PorU by the LPS transport machinery (pink) and PorZ.