Potential outer membrane protein 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 bacteria in a contact-dependent fashion. This protein may be required for secretion and assembly of the CdiA toxin protein. Inhibitory cells must be in logarithmic (not stationary) phase to inhibit growth of their targets, while the presence of P or S but not type 1 pili protects the target cells against growth inhibition. Probable member of a two partner secretion pathway (TPS) in which it mediates the secretion of CdiA. Loss of contact-dependent growth inhibition. Belongs to the TPS (TC 1.B.20) family.