Baseplate central spike complex-associated protein involved in the tail assembly. Homotrimer (PubMed:12837775, PubMed:19896486, PubMed:11823865). Heteromultimer with gp5 trimer and gp5.4 monomer; this interaction forms the tail lysozyme complex that creates an extension of the tail tube (PubMed:12837775, PubMed:27193680). The T4 tail lysozyme complex is made up of three copies of the proteolytically processed gp5 and three copies of gp27.Part of the baseplate macromolecular complex which consists of gp5, gp5.4, gp27 (central spike complex); gp6, gp25, gp53 (inner baseplate); gp7, gp8 (intermediate baseplate); gp9, gp10, gp11, gp12 (peripheral); gp48 and gp54 (proximal region of the tail tube) (PubMed:27193680). Present in 3 copies in the baseplate. Expressed in the late phase of the viral replicative cycle.