T4-gp15_tss is the tail-sheath-stabiliser or tail-terminator protein of T4-like myoviridae phage. It forms a hexamer. It simultaneously forms the binding site for attachment of the capsid to the tail as gp15 binds to gp14 and gp13, the neck proteins, and completes the tail as it binds to the top of the tail via hexamer gp3 and the C-terminal domain of gp18 located in the last ring of the contractile tail sheath [1].

1: The molecular architecture of the bacteriophage T4 neck. Fokine A, Zhang Z, Kanamaru S, Bowman VD, Aksyuk AA, Arisaka F, Rao VB, Rossmann MG; J Mol Biol. 2013;425:1731-1744. PMID:23434847