Members of this family of bacterial proteins assume a beta-sandwich structure consisting of two antiparallel beta-sheets similar to an immunoglobulin-like fold, with an additional small, antiparallel beta-sheet. The longer-stranded beta-sheet is made up of four antiparallel beta-strands. The shorter-stranded beta-sheet consists of five beta-strands, four of these beta-strands form an antiparallel beta-sheet. The exact function of this family of proteins is unknown, though a putative role includes involvement in host-bacterial interactions involved in endocytosis or phagocytosis, possibly during bacterial internalisation [1].

1: Crystal structure of a major secreted protein of Mycobacterium tuberculosis-MPT63 at 1.5-A resolution. Goulding CW, Parseghian A, Sawaya MR, Cascio D, Apostol MI, Gennaro ML, Eisenberg D; Protein Sci. 2002;11:2887-2893. PMID:12441386