1WNX

D136E mutant of Heme Oxygenase from Corynebacterium diphtheriae (HmuO)

Summary for 1WNX

• Entry DOI: 10.2210/pdb1wnx/pdb
• Related: 1IW0 1IW1 1V8X 1WNV 1WNW
• Descriptor: Heme oxygenase, SULFATE ION, SODIUM ION, ... (5 entities in total)
• Functional Keywords: heme, alpha-helix, oxidoreductase
• Biological source: Corynebacterium diphtheriae
• Total number of polymer chains: 2
• Total formula weight: 50681.03

Authors

Unno, M.,Matsui, T.,Ikeda-Saito, M. (deposition date: 2004-08-10, release date: 2004-11-09, Last modification date: 2024-05-29)

Primary citation

Matsui, T.,Furukawa, M.,Unno, M.,Tomita, T.,Ikeda-Saito, M.
Roles of Distal Asp in Heme Oxygenase from Corynebacterium diphtheriae, HmuO: A WATER-DRIVEN OXYGEN ACTIVATION MECHANISM
J.Biol.Chem., 280:2981-2989, 2005

PubMed Abstract: Heme oxygenases found in mammals, plants, and bacteria catalyze degradation of heme using the same mechanism. Roles of distal Asp (Asp-136) residue in HmuO, a heme oxygenase of Corynebacterium diphtheriae, have been investigated by site-directed mutagenesis, enzyme kinetics, resonance Raman spectroscopy, and x-ray crystallography. Replacements of the Asp-136 by Ala and Phe resulted in reduced heme degradation activity due to the formation of ferryl heme, showing that the distal Asp is critical in HmuO heme oxygenase activity. D136N HmuO catalyzed heme degradation at a similar efficiency to wild type and D136E HmuO, implying that the carboxylate moiety is not required for the heme catabolism by HmuO. Resonance Raman results suggest that the inactive ferryl heme formation in the HmuO mutants is induced by disruption of the interaction between a reactive Fe-OOH species and an adjacent distal pocket water molecule. Crystal structural analysis of the HmuO mutants confirms partial disappearance of this nearby water in D136A HmuO. Our results provide the first experimental evidence for the catalytic importance of the nearby water molecule that can be universally critical in heme oxygenase catalysis and propose that the distal Asp helps in positioning the key water molecule at a position suitable for efficient activation of the Fe-OOH species.

PubMed: 15528205
DOI: 10.1074/jbc.M410263200

Experimental method

X-RAY DIFFRACTION (1.85 Å)