1ix3

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{{STRUCTURE_1ix3| PDB=1ix3 | SCENE= }}
{{STRUCTURE_1ix3| PDB=1ix3 | SCENE= }}
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'''Crystal Structure of Rat Heme Oxygenase-1 in complex with Heme bound to Cyanide'''
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===Crystal Structure of Rat Heme Oxygenase-1 in complex with Heme bound to Cyanide===
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==Overview==
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Heme oxygenase (HO) catalyzes heme degradation by utilizing O(2) and reducing equivalents to produce biliverdin IX alpha, iron, and CO. To avoid product inhibition, the heme[bond]HO complex (heme[bond]HO) is structured to markedly increase its affinity for O(2) while suppressing its affinity for CO. We determined the crystal structures of rat ferrous heme[bond]HO and heme[bond]HO bound to CO, CN(-), and NO at 2.3, 1.8, 2.0, and 1.7 A resolution, respectively. The heme pocket of ferrous heme-HO has the same conformation as that of the previously determined ferric form, but no ligand is visible on the distal side of the ferrous heme. Fe[bond]CO and Fe[bond]CN(-) are tilted, whereas the Fe[bond]NO is bent. The structure of heme[bond]HO bound to NO is identical to that bound to N(3)(-), which is also bent as in the case of O(2). Notably, in the CO- and CN(-)-bound forms, the heme and its ligands shift toward the alpha-meso carbon, and the distal F-helix shifts in the opposite direction. These shifts allow CO or CN(-) to bind in a tilted fashion without a collision between the distal ligand and Gly139 O and cause disruption of one salt bridge between the heme and basic residue. The structural identity of the ferrous and ferric states of heme[bond]HO indicates that these shifts are not produced on reduction of heme iron. Neither such conformational changes nor a heme shift occurs on NO or N(3)(-) binding. Heme[bond]HO therefore recognizes CO and O(2) by their binding geometries. The marked reduction in the ratio of affinities of CO to O(2) for heme[bond]HO achieved by an increase in O(2) affinity [Migita, C. T., Matera, K. M., Ikeda-Saito, M., Olson, J. S., Fujii, H., Yoshimura, T., Zhou, H., and Yoshida, T. (1998) J. Biol. Chem. 273, 945-949] is explained by hydrogen bonding and polar interactions that are favorable for O(2) binding, as well as by characteristic structural changes in the CO-bound form.
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(as it appears on PubMed at http://www.pubmed.gov), where 12924938 is the PubMed ID number.
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{{ABSTRACT_PUBMED_12924938}}
==About this Structure==
==About this Structure==
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[[Category: Hemeprotein]]
[[Category: Hemeprotein]]
[[Category: Inhibitor complex]]
[[Category: Inhibitor complex]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 14:09:16 2008''

Revision as of 11:09, 1 July 2008

Image:1ix3.png

Template:STRUCTURE 1ix3

Crystal Structure of Rat Heme Oxygenase-1 in complex with Heme bound to Cyanide

Template:ABSTRACT PUBMED 12924938

About this Structure

1IX3 is a Single protein structure of sequence from Rattus norvegicus. Full crystallographic information is available from OCA.

Reference

Crystal structures of ferrous and CO-, CN(-)-, and NO-bound forms of rat heme oxygenase-1 (HO-1) in complex with heme: structural implications for discrimination between CO and O2 in HO-1., Sugishima M, Sakamoto H, Noguchi M, Fukuyama K, Biochemistry. 2003 Aug 26;42(33):9898-905. PMID:12924938

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