Crystal structure of rat heme oxygenase-1 in complex with heme

Heme oxygenase catalyzes the oxidative cleavage of protoheme to biliverdin, the first step of heme metabolism utilizing O-2 and NADPH, We determined t he crystal structures of rat heme oxygenase-1 (HO-1)-heme and selenomethion yl HO-1-heme complexes. Heme is sandwiched between two helices with the del ta-meso edge of the heme being exposed to the surface. Gly143N forms a hydr ogen bond to the distal ligand of heme, OH-. The distance between Gly143N a nd the ligand is shorter than that in the human HO-1-heme complex, This dif ference may be related to a pH-dependent change of the distal ligand of hem e, Flexibility of the distal helix may control the stability of the coordin ation of the distal ligand to heme iron. The possible role of Gly143 in the heme oxygenase reaction is discussed. (C) 2000 Federation of European Bioc hemical Societies.