Members of this protein family are restricted to the Proteobacteria. Each contains a C-terminal sortase-recognition motif, transmembrane domain, and basic residues cluster at the the C-terminus, and is encoded adjacent to a sortase gene. This protein is frequently the only sortase target in its genome, which is as unusual its occurrence in Gram-negative rather than Gram-positive genomes. Many bacteria with this system are marine. In addition to the LPXTG signal, members carry a vault protein inter-alpha-trypsin inhibitor domain (pfam08487) and a von Willebrand factor type A domain (pfam00092).
Jiyao W et al.(2023). "The conserved domain database in 2023.",