The degradation of heme in mammalian cells is catalyzed by the enzyme heme oxygenase (HO). The products of HO activity play important physiological functions: CO is believed to play a role similar to that of NO in signal transduction and communication. Biliverdin is the source of bilirubin, a powerful antioxidant. The catalytic cycle of HO parallels that of cyt P450 and other monooxygenases in that both types of enzyme form a ferric hydroperoxide (FeIII-OOH) intermediate. Whereas the FeIII-OOH intermediate in HO attacks the heme in order to form meso-hydroxyheme, the FeIII-OOH intermediate in monooxygenases andperoxidases decays into a ferryl (FeIV=O) Intermeidate. Consequently, the elucidation of the mechanism of action of HO is not only expected to contribute information regarding heme catabolism, but it will also provide information regarding the broader issue of O2 activation at heme centers. The overall objective of the proposed studies is to determine fundamental aspects of hem catabolism with an emphasis on delineating structural and electronic aspects that dictate the reactivity of key intermediates in the pathway of hem degradation. To these ends we will conduct the following research: 1) Conduct 1H and 13C NMR spectroscopic studies in order to determine the electronic configuration of low-spin ferric hemes coordinate by a hydroperoxy axial ligand. 2) Investigate the effect of the electronic structure of the FeIII-OOH intermediate on the regioselectivity of heme oxygenation. 3) Investigate the fundamental aspects underlying the conversion of verdoheme to biliverdin. In order to accomplish this goal we will carry out NMR spectroscopic experiments with the verdoheme complex of hem oxygenase and with the verdoheme complex of a mutant of hem oxygenase not capable of oxidizing verdoheme to biliverdin. Parallel studies willb e carried out with mutants of mitochondrial cytochrome b5 that can and cannot oxidize verdoheme to biliverdin.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM050503-09
Application #
6774763
Study Section
Metallobiochemistry Study Section (BMT)
Program Officer
Preusch, Peter C
Project Start
1995-04-01
Project End
2006-06-30
Budget Start
2004-07-01
Budget End
2006-06-30
Support Year
9
Fiscal Year
2004
Total Cost
$247,833
Indirect Cost
Name
University of Kansas Lawrence
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
076248616
City
Lawrence
State
KS
Country
United States
Zip Code
66045
Benson, David R; Rivera, Mario (2013) Heme uptake and metabolism in bacteria. Met Ions Life Sci 12:279-332
Yao, Huili; Jepkorir, Grace; Lovell, Scott et al. (2011) Two distinct ferritin-like molecules in Pseudomonas aeruginosa: the product of the bfrA gene is a bacterial ferritin (FtnA) and not a bacterioferritin (Bfr). Biochemistry 50:5236-48
Weeratunga, Saroja K; Lovell, Scott; Yao, Huili et al. (2010) Structural studies of bacterioferritin B from Pseudomonas aeruginosa suggest a gating mechanism for iron uptake via the ferroxidase center . Biochemistry 49:1160-75
Yukl, Erik T; Jepkorir, Grace; Alontaga, Aileen Y et al. (2010) Kinetic and spectroscopic studies of hemin acquisition in the hemophore HasAp from Pseudomonas aeruginosa. Biochemistry 49:6646-54
Jepkorir, Grace; Rodríguez, Juan Carlos; Rui, Huan et al. (2010) Structural, NMR spectroscopic, and computational investigation of hemin loading in the hemophore HasAp from Pseudomonas aeruginosa. J Am Chem Soc 132:9857-72
Rivera, Mario; Rodríguez, Juan C (2009) The dual role of heme as cofactor and substrate in the biosynthesis of carbon monoxide. Met Ions Life Sci 6:241-93
Weeratunga, Saroja K; Gee, Casey E; Lovell, Scott et al. (2009) Binding of Pseudomonas aeruginosa apobacterioferritin-associated ferredoxin to bacterioferritin B promotes heme mediation of electron delivery and mobilization of core mineral iron. Biochemistry 48:7420-31
Alontaga, Aileen Y; Rodriguez, Juan Carlos; Schönbrunn, Ernst et al. (2009) Structural characterization of the hemophore HasAp from Pseudomonas aeruginosa: NMR spectroscopy reveals protein-protein interactions between Holo-HasAp and hemoglobin. Biochemistry 48:96-109
Wang, An; Rodriguez, Juan Carlos; Han, Huijong et al. (2008) X-ray crystallographic and solution state nuclear magnetic resonance spectroscopic investigations of NADP+ binding to ferredoxin NADP reductase from Pseudomonas aeruginosa. Biochemistry 47:8080-93