This superfamily comprises domain D3 from ORF16 characterised in phage p2 from the Siphovirida family, Caudovirales order, a virus that infects Lactococcus bacterial species. All known siphophages infecting Lactococcus lactis possess a baseplate at the tip of their tail involved in host recognition and attachment and consists of several proteins derived from consecutive open-reading-frames, including ORF16. ORF16 is one of the most well-conserved protein among lactococcal phages. It is a four-domain protein that adopts a similar fold to gp27 in myophage T4.

PFAM:PF16792, INTERPRO:IPR031861,PMID:20351260;