INOR 941 |
| Nitric oxide reductase (NOR) is the enzyme in the denitrification cycle that catalyzes the two electron reduction of NO to N2O. Heme-copper oxidases (HCOs) are large membrane-bound proteins that catalyze the proton-coupled reduction of O2 to water. Despite their different reactivities, all six His metal ligands in the active site of HCOs are conserved in bacterial NOR at the same predicted positions in the 12 trans-membrane helices of HCOs. However, the metal site in HCOs (CuB) has been replaced by a non-heme iron binding site (FeB) in NOR. We have engineered a CuB site into myoglobin (CuBMb) and investigated its reactivity towards nitric oxide in the presence of Cu(I) and Zn(II). We show that CuBMb is capable of catalytically reducing NO to N2O in the presence of Cu(I), but not Zn(II). Additionally, EPR spectroscopy shows the formation of a six-coordinate His-heme-NO species in the presence of Cu(I), and breakage of the heme-His bond to from a five-coordinate species in the presence of Zn(II). Therefore, the identity and charge of the metal ion in CuBMb is important towards NO reduction.
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Bioinorganic Modeling
1:30 PM-5:30 PM, Wednesday, 13 September 2006 Moscone Center -- Room 307, Oral
Division of Inorganic Chemistry |
