Disruption of an Active Site Hydrogen Bond Converts Human Heme Oxygenase-1 into a Peroxidase

Luke Koenigs Lightning, Hong Wei Huang, Pierre Moënne-Loccoz, Thomas M. Loehr, David J. Schuller, Thomas L. Poulos, Paul R. Ortiz De Montellano

Research output: Contribution to journalArticlepeer-review

90 Scopus citations


The crystal structure of heme oxygenase-1 suggests that Asp-140 may participate in a hydrogen bonding network involving ligands coordinated to the heme iron atom. To examine this possibility, Asp-140 was mutated to an alanine, phenylalanine, histidine, leucine, or asparagine, and the properties of the purified proteins were investigated. UV-visible and resonance Raman spectroscopy indicate that the distal water ligand is lost from the iron in all the mutants except, to some extent, the D140N mutant. In the D140H mutant, the distal water ligand is replaced by the new His-140 as the sixth iron ligand, giving a bis-histidine complex. The D140A, D140H, and D140N mutants retain a trace (<3%) of biliverdin forming activity, but the D140F and D140L mutants are inactive in this respect. However, the two latter mutants retain a low ability to form verdoheme, an intermediate in the reaction sequence. All the Asp-140 mutants exhibit a new peroxidase activity. The results indicate that disruption of the distal hydrogen bonding environment by mutation of Asp-140 destabilizes the ferrous dioxygen complex and promotes conversion of the ferrous hydroperoxy intermediate obtained by reduction of the ferrous dioxygen complex to a ferryl species at the expense of its normal reaction with the porphyrin ring.

Original languageEnglish (US)
Pages (from-to)10612-10619
Number of pages8
JournalJournal of Biological Chemistry
Issue number14
StatePublished - Apr 6 2001

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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