This is a family of Gram-negative bacterial proteins that form part of the type VI pathogenicity secretion system (T6SS), including TssG. TssG is homologues to phage tail proteins and is required for proper assembly of the Hcp tube in bacteria [5].One other member in this family, SciB (Q93IT4) from Salmonella enterica, is thought to be involved in virulence [1].

1: The Salmonella enterica subspecies I specific centisome 7 genomic island encodes novel protein families present in bacteria living in close contact with eukaryotic cells. Folkesson A, Lofdahl S, Normark S; Res Microbiol 2002;153:537-545. PMID:12437215

2: Hcp family proteins secreted via the type VI secretion system coordinately regulate Escherichia coli K1 interaction with human brain microvascular endothelial cells. Zhou Y, Tao J, Yu H, Ni J, Zeng L, Teng Q, Kim KS, Zhao GP, Guo X, Yao Y; Infect Immun. 2012;80:1243-1251. PMID:22184413

3: Type VI secretion: a beginner's guide. Bingle LE, Bailey CM, Pallen MJ; Curr Opin Microbiol. 2008;11:3-8. PMID:18289922

4: The rise of the Type VI secretion system. Filloux A; F1000Prime Rep. 2013;5:52. PMID:24381728

5: The Type VI Secretion TssEFGK-VgrG Phage-Like Baseplate Is Recruited to the TssJLM Membrane Complex via Multiple Contacts and Serves As Assembly Platform for Tail Tube/Sheath Polymerization. Brunet YR, Zoued A, Boyer F, Douzi B, Cascales E; PLoS Genet. 2015;11:e1005545. PMID:26460929