TraB/PrgY proteins, identified in gut bacterium Enterococcus faecalis, are plasmid-borne homologs that are induced by pheromones. Induction rends the host bacterium insensitive to self-induction by its own pheromones, and prevents the transfer of the pheromone-inducible conjugative plasmids to bacteria that already contain it. Based on homology to Tiki activity, it has been proposed that TraB acts as a protease in the inactivation of mating pheromone, cleaving at the amino-terminus. The pheromones are small peptides (7-8 residues) encoded by the bacterial genome, and are specific for particular plasmids, or class of plasmids, which may contain several virulence factors and disseminate rapidly. Plasmid-borne antibiotic resistance and virulence determinants make these elements important contributors to medical problems. Trab/PrygY is a member of a Tiki-like superfamily. Tiki is a membrane-associated metalloprotease (MEROPS family M96) that inhibits Wnt via the cleavage of its amino terminus. Wnt is essential in animal development and homeostasis. In Xenopus, Tiki is critical in head development. In human cells, Tiki inhibits Wnt-signaling. Tiki proteins are also related to erythromycin esterase, gumN plant pathogens, RtxA containing toxins, and Campylobacter Jejuni ChaN heme-binding protein.
Jiyao W et al.(2023). "The conserved domain database in 2023.",