1iw1
Crystal structure of a heme oxygenase (HmuO) from Corynebacterium diphtheriae complexed with heme in the ferrous state
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OverviewOverview
Crystal structures of the ferric and ferrous heme complexes of HmuO, a, 24-kDa heme oxygenase of Corynebacterium diphtheriae, have been refined to, 1.4 and 1.5 A resolution, respectively. The HmuO structures show that the, heme group is closely sandwiched between the proximal and distal helices., The imidazole group of His-20 is the proximal heme ligand, which closely, eclipses the beta- and delta-meso axis of the porphyrin ring. A long range, hydrogen bonding network is present, connecting the iron-bound water, ligand to the solvent water molecule. This enables proton transfer from, the solvent to the catalytic site, where the oxygen activation occurs. In, comparison to the ferric complex, the proximal and distal helices move, closer to the heme plane in the ferrous complex. Together with the kinked, distal helix, this movement leaves only the alpha-meso carbon atom, accessible to the iron-bound dioxygen. The heme pocket architecture is, responsible for stabilization of the ferric hydroperoxo-active, intermediate by preventing premature heterolytic O-O bond cleavage. This, allows the enzyme to oxygenate selectively at the alpha-meso carbon in, HmuO catalysis.
About this StructureAbout this Structure
1IW1 is a Single protein structure of sequence from Corynebacterium diphtheriae with SUC, SO4 and HEM as ligands. Active as Heme oxygenase, with EC number 1.14.99.3 Full crystallographic information is available from OCA.
ReferenceReference
The crystal structures of the ferric and ferrous forms of the heme complex of HmuO, a heme oxygenase of Corynebacterium diphtheriae., Hirotsu S, Chu GC, Unno M, Lee DS, Yoshida T, Park SY, Shiro Y, Ikeda-Saito M, J Biol Chem. 2004 Mar 19;279(12):11937-47. Epub 2003 Nov 26. PMID:14645223
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