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Title
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An iron hydroxide moiety in the 1.35 A resolution structure of hydrogen peroxide derived myoglobin compound II at pH 5.2.
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Authors
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H.P.Hersleth,
B.Dalhus,
C.H.Görbitz,
K.K.Andersson.
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Ref.
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J Biol Inorg Chem, 2002,
7,
299-304.
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PubMed id
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Abstract
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The biological conversions of O(2) and peroxides to water as well as certain
incorporations of oxygen atoms into small organic molecules can be catalyzed by
metal ions in different clusters or cofactors. The catalytic cycle of these
reactions passes through similar metal-based complexes in which one oxygen- or
peroxide-derived oxygen atom is coordinated to an oxidized form of the catalytic
metal center. In haem-based peroxidases or oxygenases the ferryl (Fe(IV)O) form
is important in compound I and compound II, which are two and one oxidation
equivalents higher than the ferric (Fe(III)) form, respectively. In this study
we report the 1.35 A structure of a compound II model protein, obtained by
reacting hydrogen peroxide with ferric myoglobin at pH 5.2. The molecular
geometry is virtually unchanged compared to the ferric form, indicating that
these reactive intermediates do not undergo large structural changes. It is
further suggested that at low pH the dominating compound II resonance form is a
hydroxyl radical ferric iron rather than an oxo-ferryl form, based on the short
hydrogen bonding to the distal histidine (2.70 A) and the Fe...O distance. The
1.92 A Fe...O distance is in agreement with an EXAFS study of compound II in
horseradish peroxidase.
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