Family member Shigella flexneri VirK (Swiss:Q99QA5) is a virulence protein required for the expression, or correct membrane localisation of IcsA (VirG) on the bacterial cell surface [1], [2]. This family also includes Pasteurella haemolytica lapB (Swiss:P32181), which is thought to be membrane-associated.

1: Identification and characterization of virK, a virulence-associated large plasmid gene essential for intercellular spreading of Shigella flexneri. Nakata N, Sasakawa C, Okada N, Tobe T, Fukuda I, Suzuki T, Komatsu K, Yoshikawa M; Mol Microbiol 1992;6:2387-2395. PMID:1406277

2: The virulence plasmid pWR100 and the repertoire of proteins secreted by the type III secretion apparatus of Shigella flexneri. Buchrieser C, Glaser P, Rusniok C, Nedjari H, D'Hauteville H, Kunst F, Sansonetti P, Parsot C; Mol Microbiol 2000;38:760-771. PMID:11115111