This is a family of Siphoviridae phage tail tube proteins including several from Lactococcus lactis.

1: Gene organization and transcription of a late-expressed region of a Lactococcus lactis phage. Parreira R, Valyasevi R, Lerayer AL, Ehrlich SD, Chopin MC; J Bacteriol 1996;178:6158-6165. PMID:8892814

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