Baseplate protein that is part of the baseplate wedge and that connects the short tail fibers to the baseplate (PubMed:15315755). Involved in the tail assembly. Homotrimer (PubMed:27193680, PubMed:19896486). The gp11 trimer interacts with gp10 trimer and with the short tail fiber (STF) composed of the gp12 trimer (PubMed:27193680). 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 18 copies in the baseplate. Expressed in the late phase of the viral replicative cycle.