This domain is found at the very C-terminus of bacteriophage parallel beta-helical tailspike proteins. It carries the enzymic residues that induce autoproteolytic cleavage to bring about maturation of the folding process of the helix in a chaperone-like manner. The domain thus mediates the assembly of a large tailspike protein and then releases itself after maturation. These C-terminal regions that autoproteolytically release themselves after maturation are exchangeable between functionally unrelated N-terminal proteins and have been identified in a number of bacteriophage tailspike proteins.
Jiyao W et al.(2023). "The conserved domain database in 2023.",