This family of archaeal proteins contains. an amino terminal motif QXSXEXXXL that has been suggested to be part of a class III signal sequence. With the Q being the +1 residue of the signal peptidase cleavage site. Two members of this family are cleaved by a type IV pilin-like signal peptidase.
Jiyao W et al.(2023). "The conserved domain database in 2023.",