This family of head-tail connector proteins is found in bacteria and viruses. Proteins in this family are typically between 516 and 555 amino acids in length. This protein is found in Phage T7 and T3 among others.

1: Purification of characterization of gene 8 product of bacteriophage T3. Nakasu S, Fujisawa H, Minagawa T; Virology. 1985;143:422-434. PMID:3904172