This phage protein family is expressed from within a cluster of tail- and base plate-producing genes [1]. It is a family of tail assembly chaperone proteins [2].

1: Genome and proteome of Listeria monocytogenes phage PSA: an unusual case for programmed + 1 translational frameshifting in structural protein synthesis. Zimmer M, Sattelberger E, Inman RB, Calendar R, Loessner MJ; Mol Microbiol. 2003;50:303-317. PMID:14507382

2: A conserved spiral structure for highly diverged phage tail assembly chaperones. Pell LG, Cumby N, Clark TE, Tuite A, Battaile KP, Edwards AM, Chirgadze NY, Davidson AR, Maxwell KL; J Mol Biol. 2013;425:2436-2449. PMID:23542344