This model describes a conserved domain found in surface proteins of a number of Firmutes. Many members have LPXTG C-terminal anchoring motifs and a substantial number have the KxYKxGKxW putative sorting signal at the N-terminus. The tetracycline resistance plasmid pCF10 in Enterococcus faecalis promotes conjugal plasmid transfer in response to sex pheromones, but PgrA/Sec10 encoded by that plasmid, a member of this family, specifically inhibits the ability of cells to receive homologous plasmids. The phenomenon is called surface exclusion.