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An iron hydroxide moiety in the 1.35 Å resolution structure of hydrogen peroxide derived myoglobin compound II at pH 5.2

  • H.-P. Hersleth
  • B. Dalhus
  • C. Görbitz
  • K. Andersson
Original Article

Abstract.

The biological conversions of O2 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 (FeIVO) form is important in compound I and compound II, which are two and one oxidation equivalents higher than the ferric (FeIII) form, respectively. In this study we report the 1.35 Å 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 Å) and the Fe···O distance. The 1.92 Å Fe···O distance is in agreement with an EXAFS study of compound II in horseradish peroxidase.

Myoglobin Compound II Haem Hydroxyl radical Oxygen activation 

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Copyright information

© SBIC 2001

Authors and Affiliations

  • H.-P. Hersleth
    • 2
  • B. Dalhus
    • 2
  • C. Görbitz
    • 2
  • K. Andersson
    • 1
  1. 1.Department of Biochemistry, University of Oslo, P.O. Box 1041 Blindern, 0316 Oslo, NorwayNorway
  2. 2.Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, 0315 Oslo, NorwayNorway

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