This domain is found in Uncharacterized protein MJ0754 from Methanocaldococcus jannaschii and similar proteins from bacteria and archaea. MJ0754 adopts a dimeric assembly, with each monomer consisting of six alpha-helices [1]. It is a member of a broad superfamily of ferritin-like diiron-carboxylate proteins whose function is unknown. The conserved residues of a diiron centre are present within the putative active site.

1: Structural insights into the metal binding properties of hypothetical protein MJ0754 from Methanococcus jannaschii. Lee EH, Kim HS, Kim HY, Jeon YH, Hwang KY; Proteins. 2011;79:2358-2363. PMID:21604308