We have determined the structure of rubrerythrin, a non-haem iron protein from
the anaerobic sulphate-reducing bacterium, Desulfovibrio vulgaris
(Hildenborough), by X-ray crystallography. The structure reveals a tetramer of
two-domain subunits. Each subunit contains a four-helix bundle surrounding a
diiron-oxo site and a C-terminal rubredoxin-like FeS4 domain. The diiron-oxo
site contains a larger number of carboxylate ligands and a higher degree of
solvent exposure than do those in other diiron-oxo proteins. The four-helix
bundle of rubrerythrin closely resembles those of the ferritin and
bacterioferritin subunits, suggesting a relationship among these
proteins-consistent with the recently demonstrated ferroxidase activity of
rubrerythrin.
