This is a family of putative bacterial lipoproteins necessary for the uptake of haem-iron. The structure of UniProtKB:Q0PBW2, PDB:2g5g, comprises a large parallel beta-sheet with flanking alpha-helices and a smaller domain consisting of alpha-helices. Two cofacial haem groups (~3.5 Angstom apart with an inter-iron distance of 4.4 Angstrom) bind in a pocket formed by a dimer of two ChaN monomers [1,2].

1: Tiki, at the head of a new superfamily of enzymes. Sanchez-Pulido L, Ponting CP; Bioinformatics. 2013;29:2371-2374. PMID:23868957

2: Cofacial heme binding is linked to dimerization by a bacterial heme transport protein. Chan AC, Lelj-Garolla B, I Rosell F, Pedersen KA, Mauk AG, Murphy ME; J Mol Biol. 2006;362:1108-1119. PMID:16950397