1IW0

Crystal structure of a heme oxygenase (HmuO) from Corynebacterium diphtheriae complexed with heme in the ferric state

Summary for 1IW0

• Entry DOI: 10.2210/pdb1iw0/pdb
• Related: 1IW1
• Related PRD ID: PRD_900003
• Descriptor: Heme oxygenase, beta-D-fructofuranose-(2-1)-alpha-D-glucopyranose, PROTOPORPHYRIN IX CONTAINING FE, ... (5 entities in total)
• Functional Keywords: alpha helix, bacterial iron acquisition, riken structural genomics/proteomics initiative, rsgi, structural genomics, oxidoreductase
• Biological source: Corynebacterium diphtheriae
• Total number of polymer chains: 3
• Total formula weight: 75278.61

Authors

Hirotsu, S.,Unno, M.,Chu, G.C.,Lee, D.S.,Park, S.Y.,Shiro, Y.,Ikeda-Saito, M.,RIKEN Structural Genomics/Proteomics Initiative (RSGI) (deposition date: 2002-04-04, release date: 2003-04-08, Last modification date: 2023-12-27)

Primary citation

Hirotsu, S.,Chu, G.C.,Unno, M.,Lee, D.S.,Yoshida, T.,Park, S.Y.,Shiro, Y.,Ikeda-Saito, M.
The crystal structures of the ferric and ferrous forms of the heme complex of HmuO, a heme oxygenase of Corynebacterium diphtheriae.
J.Biol.Chem., 279:11937-11947, 2004

PubMed Abstract: Crystal structures of the ferric and ferrous heme complexes of HmuO, a 24-kDa heme oxygenase of Corynebacterium diphtheriae, have been refined to 1.4 and 1.5 A resolution, respectively. The HmuO structures show that the heme group is closely sandwiched between the proximal and distal helices. The imidazole group of His-20 is the proximal heme ligand, which closely eclipses the beta- and delta-meso axis of the porphyrin ring. A long range hydrogen bonding network is present, connecting the iron-bound water ligand to the solvent water molecule. This enables proton transfer from the solvent to the catalytic site, where the oxygen activation occurs. In comparison to the ferric complex, the proximal and distal helices move closer to the heme plane in the ferrous complex. Together with the kinked distal helix, this movement leaves only the alpha-meso carbon atom accessible to the iron-bound dioxygen. The heme pocket architecture is responsible for stabilization of the ferric hydroperoxo-active intermediate by preventing premature heterolytic O-O bond cleavage. This allows the enzyme to oxygenate selectively at the alpha-meso carbon in HmuO catalysis.

PubMed: 14645223
DOI: 10.1074/jbc.M311631200

Experimental method

X-RAY DIFFRACTION (1.4 Å)