Journal of Biological Chemistry
Volume 282, Issue 52, 28 December 2007, Pages 37624-37631
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Protein Structure and Folding
Comparison of Apo- and Heme-bound Crystal Structures of a Truncated Human Heme Oxygenase-2*

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Heme oxygenase (HO) catalyzes the first step in the heme degradation pathway. The crystal structures of apo- and heme-bound truncated human HO-2 reveal a primarily α-helical architecture similar to that of human HO-1 and other known HOs. Proper orientation of heme in HO-2 is required for the regioselective oxidation of the α-mesocarbon. This is accomplished by interactions within the heme binding pocket, which is made up of two helices. The iron coordinating residue, His45, resides on the proximal helix. The distal helix contains highly conserved glycine residues that allow the helix to flex and interact with the bound heme. Tyr154, Lys199, and Arg203 orient the heme through direct interactions with the heme propionates. The rearrangements of side chains in heme-bound HO-2 compared with apoHO-2 further elucidate HO-2 heme interactions.

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The atomic coordinates and structure factors (code 2RGZ)) have been deposited in the Protein Data Bank, Research Collaboratory for Structural Bioinformatics, Rutgers University, New Brunswick, NJ (http://www.rcsb.org/).

*

The Center for Eukaryotic Structural Genomics has been funded by NIGMS, National Institutes of Health Grants 1-U54-GM074901-01 (to J. L. M.) and P50-GM064598 (to J. L. M.). Use of the Advanced Photon Source was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract DE-AC02-06CH11357. The General Medicine and Cancer Institutes Collaborative Access Team has been funded by NCI, National Institutes of Health (NIH) Grant Y1-CO-1020 and NIGMS, NIH Grant Y1-GM-1104. This work was partially supported by a Redox Biology Center seed grant from NIH Center Grant 1P2ORR17675 (to the University of Nebraska). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The on-line version of this article (available at http://www.jbc.org) contains supplemental Figs. S1 and S2.