Bacteriophages infect host cells by injecting their genome through the cell wall [1]. To this end, tailed bacteriophages have evolved complex tail machines that extend from a unique capsid vertex, providing both an attachment point to the host surface, and a channel for genome-ejection through the cell envelope [2]. Family members of this domain are putative gp17 proteins involved in genome delivery tail machine in Entereobacteria phage p22 and Salmonella phage ViI. Gp17 found in other bacteriophages such as SPP1 (siphophage SPP1, a lytic Bacillus subtilis phage) has been identified as a tail completion protein adopting an alpha/beta fold, and found to be located at the interface between the head-to-tail connector and the tail of bacteriophage SPP1 [3].

1: Molecular interactions and residues involved in force generation in the T4 viral DNA packaging motor. Migliori AD, Smith DE, Arya G; J Mol Biol. 2014;426:4002-4017. PMID:25311860

2: Architecture of viral genome-delivery molecular machines. Bhardwaj A, Olia AS, Cingolani G; Curr Opin Struct Biol. 2014;25:1-8. PMID:24878339

3: Solution structure of gp17 from the Siphoviridae bacteriophage SPP1: insights into its role in virion assembly. Chagot B, Auzat I, Gallopin M, Petitpas I, Gilquin B, Tavares P, Zinn-Justin S; Proteins. 2012;80:319-326. PMID:22072538