THE STRUCTURE OF DESULFOVIBRIO-VULGARIS RUBRERYTHRIN REVEALS A UNIQUECOMBINATION OF RUBREDOXIN-LIKE FES4 AND FERRITIN-LIKE DIIRON DOMAINS

We have determined the structure of rubrerythrin, a non-haem iron prot ein from the anaerobic sulphate-reducing bacterium, Desulfovibrio vulg aris (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 carboxyla te ligands and a higher degree of solvent exposure than do those in ot her diiron-oxo proteins. The four-helix bundle of rubrerythrin closely resembles those of the ferritin and bacterioferritin subunits, sugges ting a relationship among these proteins-consistent with the recently demonstrated ferroxidase activity of rubrerythrin.