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Publication Abstract from PubMed

HO (haem oxygenase) catalyses the degradation of haem to biliverdin, CO and ferrous iron via three successive oxygenation reactions, i.e. haem to alpha-hydroxyhaem, alpha-hydroxyhaem to alpha-verdohaem and alpha-verdohaem to ferric biliverdin-iron chelate. In the present study, we determined the crystal structure of ferrous alpha-verdohaem-rat HO-1 complex at 2.2 A (1 A=0.1 nm) resolution. The overall structure of the verdohaem complex was similar to that of the haem complex. Water or OH- was co-ordinated to the verdohaem iron as a distal ligand. A hydrogen-bond network consisting of water molecules and several amino acid residues was observed at the distal side of verdohaem. Such a hydrogen-bond network was conserved in the structures of rat HO-1 complexes with haem and with the ferric biliverdin-iron chelate. This hydrogen-bond network may act as a proton donor to form an activated oxygen intermediate, probably a ferric hydroperoxide species, in the degradation of alpha-verdohaem to ferric biliverdin-iron chelate similar to that seen in the first oxygenation step.

Crystal structure of rat haem oxygenase-1 in complex with ferrous verdohaem: presence of a hydrogen-bond network on the distal side.,Sato H, Sugishima M, Sakamoto H, Higashimoto Y, Shimokawa C, Fukuyama K, Palmer G, Noguchi M Biochem J. 2009 Apr 15;419(2):339-45. PMID:19154182^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.