1J2C: Crystal Structure Of Rat Heme Oxygenase-1 In Complex With Biliverdin Ixalpha-Iron Cluster

Citation:
Abstract
The crystal structure of rat heme oxygenase-1 in complex with biliverdin-iron chelate (biliverdin(Fe)-HO-1), the immediate precursor of the final product, biliverdin, has been determined at a 2.4-A resolution. The electron density in the heme pocket clearly showed that the tetrapyrrole ring of heme is cleaved at the alpha-meso edge. Like the heme bound to HO-1, biliverdin-iron chelate is located between the distal and proximal helices, but its accommodation state seems to be less stable in light of the disordering of the solvent-exposed propionate and vinyl groups. The middle of the distal helix is shifted away from the center of the active site in biliverdin(Fe)-HO-1, increasing the size of the heme pocket. The hydrogen-bonding interaction between Glu-29 and Gln-38, considered to restrain the orientation of the proximal helix in the heme-HO-1 complex, was lost in biliverdin(Fe)-HO-1, leading to relaxation of the helix. Biliverdin has a distorted helical conformation; the lactam oxygen atom of its pyrrole ring-A interacted with Asp-140 through a hydrogen-bonding solvent network. Because of the absence of a distal water ligand, the iron atom is five-coordinated with His-25 and four pyrrole nitrogen atoms. The coordination geometry deviates considerably from a square pyramid, suggesting that the iron may be readily dissociated. We speculate that the opened conformation of the heme pocket facilitates sequential product release, first iron then biliverdin, and that because of biliverdin's increased flexibility, iron release triggers its slow dissociation.
PDB ID: 1J2CDownload
MMDB ID: 23846
PDB Deposition Date: 2002/12/29
Updated in MMDB: 2012/11
Experimental Method:
x-ray diffraction
Resolution: 2.4  Å
Source Organism:
Similar Structures:
Biological Unit for 1J2C: monomeric; determined by author
Molecular Components in 1J2C
Label Count Molecule
Protein (1 molecule)
1
Heme Oxygenase-1(Gene symbol: Hmox1)
Molecule annotation
Chemicals (2 molecules)
1
1
2
1
* Click molecule labels to explore molecular sequence information.

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