Members of this family form a set of bacteriophage adsorption proteins, composed mainly of beta-strands whose complicated topology forms an elongated seahorse-shaped molecule with a distinct head, containing a pseudo-beta propeller structure with approximate 6-fold symmetry, and tail. They are required for the attachment of the phage to the host conjugative DNA transfer complex. This is a poorly understood large transmembrane complex of unknown architecture, with at least 11 different proteins.
Jiyao W et al.(2023). "The conserved domain database in 2023.",