Crystal structure of human heme oxygenase-1

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Heme oxygenase catalyzes the first step in the oxidative degradation of heme. The crystal structure of heme oxygenase-1 (HO-1) reported here reveals a novel helical fold with the heme sandwiched between two helices. The proximal helix provides a heme iron ligand, His 25. Conserved glycines in the distal helix near the oxygen binding site allow close contact between the helix backbone and heme in addition to providing flexibility for substrate binding and product release. Regioselective oxygenation of the α-meso heme carbon is due primarily to steric influence of the distal helix.

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Figure 1
Figure 2: The overall structure of HO-1.
Figure 3: Solvent-accessible surfaces of HO-1 colored by electrostatic potential (negative is red, positive is blue).
Figure 4: The active site of HO-1.
Figure 5: Flexibility and alternate conformations of the two molecules in the asymmetric unit.
Figure 6: a, Plot of the r.m.s. deviation of backbone atoms between the two molecules in the asymmetric unit.

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Protein Data Bank


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Thanks to S. Tajbaksh for help with protein purification, to J.P. Cartailler for help with the GRASP figures, to B. Bhaskar, W.N. Lanzilotta, H. Li, C.S. Raman, I. Sevrioukova and M. Sundaramoorthy for helpful discussions, and to A. J. Greenwood for computational assistance. This work was supported by grants from the National Institutes of Health (T.L.P. and P.R.O.d.M.) and the National Science Foundation (T.L.P.).

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Correspondence to Thomas L. Poulos.

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