This family consists of Chlamydia virulence proteins which are thought to be required for growth within mammalian cells [1]. The C-terminal domain shows distant homology to the TNF superfamily [2].

1: The structure of a plasmid of Chlamydia trachomatis believed to be required for growth within mammalian cells. Comanducci M, Ricci S, Ratti G; Mol Microbiol 1988;2:531-538. PMID:2845228

2: Structure of the Chlamydia trachomatis immunodominant antigen Pgp3. Galaleldeen A, Taylor AB, Chen D, Schuermann JP, Holloway SP, Hou S, Gong S, Zhong G, Hart PJ; J Biol Chem. 2013;288:22068-22079. PMID:23703617