This family contains bacterial and phage tail fibre assembly proteins. E.coli contains several members of this family although the function of these proteins is uncertain. Using the lambda phage members as examples, there are both gptfa and gpK tail proteins here. GpK forms part of the TTC or tail-tip complex that is located at the distal end of the tail. TTCs form the platform on which the tail-tube proteins self-assemble and are also the attachment point for fibers or receptor-binding proteins that mediate phage-adsorption to the surface of the host cell. TTC assembly starts with gpJ, which is also known as the central tail fibre and is involved in host-cell adsorption. It is the C-terminus of gpJ that interacts with the lamB receptor on host cells. A number of intermediates including gpK then interact with gpJ during tail morphogenesis.