This family represents a conserved region approximately 200 residues long within a number of bacterial hypersensitivity response secretion protein HrpJ and similar proteins. HrpJ forms part of a type III secretion system through which, in phytopathogenic bacterial species, virulence factors are thought to be delivered to plant cells [1]. This family also includes the InvE invasion protein from Salmonella. This protein is involved in host parasite interactions and mutations in the InvE gene render Salmonella typhimurium non-invasive [2]. InvE S. typhimurium mutants fail to elicit a rapid Ca2+ increase in cultured cells, an important event in the infection procedure and internalisation of S. typhimurium into epithelial cells [2]. This family includes bacterial SepL and SsaL proteins. SepL plays an essential role in the infection process of enterohemorrhagic Escherichia coli and is thought to be responsible for the secretion of EspA, EspD, and EspB [3]. SsaL of Salmonella typhimurium is thought to be a component of the type III secretion system [4].

1: Role of the Hrp type III protein secretion system in growth of Pseudomonas syringae pv. syringae B728a on host plants in the field. Hirano SS, Charkowski AO, Collmer A, Willis DK, Upper CD; Proc Natl Acad Sci U S A 1999;96:9851-9856. PMID:10449783

2: Identification and molecular characterization of a Salmonella typhimurium gene involved in triggering the internalization of salmonellae into cultured epithelial cells. Ginocchio C, Pace J, Galan JE; Proc Natl Acad Sci U S A 1992;89:5976-5980. PMID:1631083

3: Characterization of SepL of enterohemorrhagic Escherichia coli. Kresse AU, Beltrametti F, Muller A, Ebel F, Guzman CA; J Bacteriol 2000;182:6490-6498. PMID:11053395

4: Functional analysis of ssaJ and the ssaK/U operon, 13 genes encoding components of the type III secretion apparatus of Salmonella Pathogenicity Island 2. Hensel M, Shea JE, Raupach B, Monack D, Falkow S, Gleeson C, Kubo T, Holden DW; Mol Microbiol 1997;24:155-167. PMID:9140973