This protein family, specific to Chlamydiales, includes CT_584 from Chlamydia trachomatis, a type III secretion system (T3SS)-associated protein. This protein shows a four alpha-helix bundle at the N terminus, a three-stranded antiparallel beta-sheet, and two alpha- helices arranged in a kinked antiparallel manner at the C terminus [1].

1: Structure of CT584 from Chlamydia trachomatis refined to 3.05 A resolution. Barta ML, Hickey J, Kemege KE, Lovell S, Battaile KP, Hefty PS; Acta Crystallogr Sect F Struct Biol Cryst Commun. 2013;69:1196-1201. PMID:24192348