The IsdG-family of haem oxygenases degrades haem to a novel chromophore.

Reniere ML, Ukpabi GN, Harry SR, Stec DF, Krull R, Wright DW, Bachmann BO, Murphy ME, Skaar EP
Mol Microbiol. 2010 75 (6): 1529-38

PMID: 20180905 · PMCID: PMC3800195 · DOI:10.1111/j.1365-2958.2010.07076.x

Enzymatic haem catabolism by haem oxygenases is conserved from bacteria to humans and proceeds through a common mechanism leading to the formation of iron, carbon monoxide and biliverdin. The first members of a novel class of haem oxygenases were recently identified in Staphylococcus aureus (IsdG and IsdI) and were termed the IsdG-family of haem oxygenases. Enzymes of the IsdG-family form tertiary structures distinct from those of the canonical haem oxygenase family, suggesting that IsdG-family members degrade haem via a unique reaction mechanism. Herein we report that the IsdG-family of haem oxygenases degrade haem to the oxo-bilirubin chromophore staphylobilin. We also present the crystal structure of haem-bound IsdI in which haem ruffling and constrained binding of oxygen is consistent with cleavage of the porphyrin ring at the beta- or delta-meso carbons. Combined, these data establish that the IsdG-family of haem oxygenases degrades haem to a novel chromophore distinct from biliverdin.

MeSH Terms (11)

Bacterial Proteins Crystallography, X-Ray Heme Heme Oxygenase (Decyclizing) Mixed Function Oxygenases Models, Molecular Molecular Structure Oxidation-Reduction Oxygenases Protein Structure, Tertiary Staphylococcus aureus

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