PDBsum entry 1xk1

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protein ligands links
Oxidoreductase PDB id
Protein chains
214 a.a. *
HEM ×2
Waters ×120
* Residue conservation analysis
PDB id:
Name: Oxidoreductase
Title: Crystal structures of the g139a, g139a-no and g143h mutants of human heme oxygenase-1
Structure: Heme oxygenase 1. Chain: a, b. Synonym: ho-1. Engineered: yes. Mutation: yes
Source: Homo sapiens. Human. Organism_taxid: 9606. Gene: hmox1, ho1, ho. Expressed in: escherichia coli. Expression_system_taxid: 562
2.08Å     R-factor:   0.271    
Authors: L.Lad,P.R.Ortiz De Montellano,T.L.Poulos
Key ref: L.Lad et al. (2005). Crystal structures of the G139A, G139A-NO and G143H mutants of human heme oxygenase-1. A finely tuned hydrogen-bonding network controls oxygenase versus peroxidase activity. J Biol Inorg Chem, 10, 138-146. PubMed id: 15690204
26-Sep-04     Release date:   13-Dec-05    
Go to PROCHECK summary

Protein chains
Pfam   ArchSchema ?
P09601  (HMOX1_HUMAN) -  Heme oxygenase 1
288 a.a.
214 a.a.*
Key:    PfamA domain  Secondary structure  CATH domain
* PDB and UniProt seqs differ at 2 residue positions (black crosses)

 Enzyme reactions 
   Enzyme class: E.C.  - Heme oxygenase (biliverdin-producing).
[IntEnz]   [ExPASy]   [KEGG]   [BRENDA]
      Reaction: Protoheme + 3 AH2 + 3 O2 = biliverdin + Fe2+ + CO + 3 A + 3 H2O
Bound ligand (Het Group name = HEM)
matches with 95.00% similarity
+ 3 × AH(2)
+ 3 × O(2)
= biliverdin
+ Fe(2+)
+ CO
+ 3 × A
+ 3 × H(2)O
Molecule diagrams generated from .mol files obtained from the KEGG ftp site
 Gene Ontology (GO) functional annotation 
  GO annot!
  Biological process     oxidation-reduction process   2 terms 
  Biochemical function     heme oxygenase (decyclizing) activity     1 term  


J Biol Inorg Chem 10:138-146 (2005)
PubMed id: 15690204  
Crystal structures of the G139A, G139A-NO and G143H mutants of human heme oxygenase-1. A finely tuned hydrogen-bonding network controls oxygenase versus peroxidase activity.
L.Lad, A.Koshkin, Montellano, T.L.Poulos.
Conserved glycines, Gly139 and Gly143, in the distal helix of human heme oxygenase-1 (HO-1) provide the flexibility required for the opening and closing of the heme active site for substrate binding and product dissociation during HO-1 catalysis. Earlier mutagenesis work on human HO-1 showed that replacement of either Gly139 or Gly143 suppresses heme oxygenase activity and, in the case of the Gly139 mutants, increases peroxidase activity (Liu et al. in J. Biol. Chem. 275:34501, 2000). To further investigate the role of the conserved distal helix glycines, we have determined the crystal structures of the human HO-1 G139A mutant, the G139A mutant in a complex with NO, and the G143H mutant at 1.88, 2.18 and 2.08 A, respectively. The results confirm that fine tuning of the previously noted active-site hydrogen-bonding network is critical in determining whether heme oxygenase or peroxidase activity is observed.

Literature references that cite this PDB file's key reference

  PubMed id Reference
21157922 L.Zhou, Y.Liu, C.Zou, N.Ma, Y.Hui, G.Lv, H.Zhang, H.Zhou, and X.Gao (2011).
The effect of the Gly139His, Gly143His, and Ser142His mouse heme oxygenase-1 mutants on the HO reaction in vivo and in vitro.
  Anat Rec (Hoboken), 294, 112-118.  
17534530 M.Unno, T.Matsui, and M.Ikeda-Saito (2007).
Structure and catalytic mechanism of heme oxygenase.
  Nat Prod Rep, 24, 553-570.  
16804678 H.Li, J.Igarashi, J.Jamal, W.Yang, and T.L.Poulos (2006).
Structural studies of constitutive nitric oxide synthases with diatomic ligands bound.
  J Biol Inorg Chem, 11, 753-768.
PDB codes: 2g6h 2g6i 2g6j 2g6k 2g6l 2g6m 2g6n 2g6o
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