This is a family of bacterial and archaeal proteins, the structure for one of whose members has been characterised. PDB:3kop from Swiss:A0JVT3 probably adopts a new hexameric form compared to previous structures. The putative active is near the domain interface. 3kop is most closely related, structurally to PDB:1zx8, where the potential active site is located near residues E51 and Y53 (conserved in 1zx8). Beyond the two residues above, the other residues are not conserved. Also the shape of the active site differs from that of 1zx8. PDB:1zx8 belongs to family DUF369. Pfam:PF04126, which is part of the cyclophilin-like clan.