This family contains both viral and bacterial proteins which are related to the Gp157 protein of the Streptococcus thermophilus SFi bacteriophages. It is thought that bacteria possessing the gene coding for this protein have an increased resistance to the bacteriophage[1].

1: A short noncoding viral DNA element showing characteristics of a replication origin confers bacteriophage resistance to Streptococcus thermophilus. Foley S, Lucchini S, Zwahlen MC, Brussow H; Virology 1998;250:377-387. PMID:9792848