This family consists of several bacterial and phage proteins of around 130 residues in length which seem to be related to the bacteriophage P2 GpU protein (Swiss:O64315) which is thought to be involved in tail assembly [1].

1: Programmed translational frameshift in the bacteriophage P2 FETUD tail gene operon. Christie GE, Temple LM, Bartlett BA, Goodwin TS; J Bacteriol 2002;184:6522-6531. PMID:12426340