Members of this family are predominantly found in the F1 capsule antigen Caf1 synthesised by Yersinia bacteria. They adopt a structure consisting of a seven strands arranged in two beta-sheets, in a Greek-key topology, and mediate targeting of the bacterium to sites of infection [1].

1: Structure and biogenesis of the capsular F1 antigen from Yersinia pestis: preserved folding energy drives fiber formation. Zavialov AV, Berglund J, Pudney AF, Fooks LJ, Ibrahim TM, MacIntyre S, Knight SD; Cell. 2003;113:587-596. PMID:12787500