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. Expression of this cdiAIB locus in B.thailandensis confers protection against other bacteria carrying the locus; growth inhibition requires cellular contact. Probable member of a two partner secretion pathway (TPS) in which it mediates the secretion of CdiA2. Deletion of this gene from the locus expressed in B.thailandensis abrogates growth inhibition. Belongs to the TPS (TC 1.B.20) family.