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'''Crystal Structure of Rat Heme Oxygenase-1 in complex with Heme bound to Cyanide''' | '''Crystal Structure of Rat Heme Oxygenase-1 in complex with Heme bound to Cyanide''' | ||
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[[Category: Sakamoto, H.]] | [[Category: Sakamoto, H.]] | ||
[[Category: Sugishima, M.]] | [[Category: Sugishima, M.]] | ||
[[Category: | [[Category: Co-analog complex]] | ||
[[Category: | [[Category: Hemeprotein]] | ||
[[Category: | [[Category: Inhibitor complex]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 20:31:45 2008'' | |||
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Revision as of 20:31, 2 May 2008
Crystal Structure of Rat Heme Oxygenase-1 in complex with Heme bound to Cyanide
OverviewOverview
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.
About this StructureAbout this Structure
1IX3 is a Single protein structure of sequence from Rattus norvegicus. Full crystallographic information is available from OCA.
ReferenceReference
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 Page seeded by OCA on Fri May 2 20:31:45 2008