It is an intramembrane aspartyl protease with the conserved active site motifs 'YD' and 'GxGD' in adjacent transmembrane domains (TMDs).
A nine amino acid-long cleavage fragment is then presented on HLA-E receptors and modulates the activity of natural killer cells.
Type IV pilin is a protein found on the surface of Pseudomonas aeruginosa, Neisseria gonorrhoeae and other Gram-negative pathogens.
They are synthesised as prepilin subunits, which differ from mature pilin by virtue of containing a 6-8 residue leader peptide consisting of charged amino acids.
Following removal of the leader peptides, the same enzyme is responsible for the second posttranslational modification that characterises the type-IV pilins and their homologues, namely N-methylation of the newly exposed N-terminal amino acid residue.