This family contains bacterial and phage tail fibre assembly proteins [1]. 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 [2]. 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 fibres 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 [3].

1: DNA sequences of the tail fiber genes of bacteriophage P2: evidence for horizontal transfer of tail fiber genes among unrelated bacteriophages. Haggard-Ljungquist E, Halling C, Calendar R; J Bacteriol 1992;174:1462-1477. PMID:1531648

2: The phage lambda major tail protein structure reveals a common evolution for long-tailed phages and the type VI bacterial secretion system. Pell LG, Kanelis V, Donaldson LW, Howell PL, Davidson AR; Proc Natl Acad Sci U S A. 2009;106:4160-4165. PMID:19251647

3: The C-terminal portion of the tail fiber protein of bacteriophage lambda is responsible for binding to LamB, its receptor at the surface of Escherichia coli K-12. Wang J, Hofnung M, Charbit A; J Bacteriol. 2000;182:508-512. PMID:10629200