Heme oxygenase (HO) catalyzes the conversion of heme to biliverdin, CO, and iron. The two isoforms, HO1 and HO2, share similar physical and kinetic properties but exhibit different physiological roles and organ locations. The structures of the core catalytic domains of HO1 and HO2 are nearly superimposable and the major distinction between these HO isoforms is the occurrence of heme regulatory motifs (HRMs) in HO2 that are lacking in HO1. The HRMs play a regulatory role as a thiol/disulfide redox switch that we have shown to regulate interactions of HO2 with substrate (heme) and with a Ca++- activated high conductance potassium channel (the BK or Slopoke channel). Regulation of K+ flux across the membrane by the BK channel enables the O2 sensing function of the carotid body, which controls respiratory system ventilation in response to changes in the blood oxygen concentration. We recently demonstrated that the BK channel also contains a thiol/disulfide redox switch that regulates binding of heme, which has been shown to control its K+ channel activity. We plan to use spectroscopic, kinetic, genetic, crystallographic, NMR, and electrophysiology methods to determine how these thiol/disulfide redox switches (the HRMs in human HO2 and the CXXC motif in the human BK channel) affect the structure and function of and interactions between these functionally linked proteins. We will determine the redox states of the heme and HRMs in vitro and in vivo under various physiological conditions. We also will perform spectroscopic and electrophysiology measurements to determine the mechanism by which HO2 influences BK channel function.

Public Health Relevance

Heme oxygenase (HO) is the only mammalian protein known to degrade heme and sits at the nexus of several major redox and metal regulatory systems. Unlike HO1, HO2 contains two Heme Regulatory Motifs (HRMs) that form a thiol/disulfide redox switch, which regulates binding of its substrate, heme. We propose to determine how thiol/disulfide redox switches on HO2 and on a functionally related interacting partner, a heme-regulated potassium channel, regulate their structures and functions.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL102662-04
Application #
8501649
Study Section
Macromolecular Structure and Function A Study Section (MSFA)
Program Officer
Chang, Henry
Project Start
2010-07-01
Project End
2014-06-30
Budget Start
2013-07-01
Budget End
2014-06-30
Support Year
4
Fiscal Year
2013
Total Cost
$531,351
Indirect Cost
$189,646
Name
University of Michigan Ann Arbor
Department
Biochemistry
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Carter, Eric L; Gupta, Nirupama; Ragsdale, Stephen W (2016) High Affinity Heme Binding to a Heme Regulatory Motif on the Nuclear Receptor Rev-erb? Leads to Its Degradation and Indirectly Regulates Its Interaction with Nuclear Receptor Corepressor. J Biol Chem 291:2196-222
Davydov, Roman; Fleischhacker, Angela S; Bagai, Ireena et al. (2016) Comparison of the Mechanisms of Heme Hydroxylation by Heme Oxygenases-1 and -2: Kinetic and Cryoreduction Studies. Biochemistry 55:62-8
Fleischhacker, Angela S; Sharma, Ajay; Choi, Michelle et al. (2015) The C-terminal heme regulatory motifs of heme oxygenase-2 are redox-regulated heme binding sites. Biochemistry 54:2709-18
Carter, Eric L; Ragsdale, Stephen W (2014) Modulation of nuclear receptor function by cellular redox poise. J Inorg Biochem 133:92-103
Spencer, Andrea L M; Bagai, Ireena; Becker, Donald F et al. (2014) Protein/protein interactions in the mammalian heme degradation pathway: heme oxygenase-2, cytochrome P450 reductase, and biliverdin reductase. J Biol Chem 289:29836-58
Zuiderweg, Erik R P; Bagai, Ireena; Rossi, Paolo et al. (2013) EZ-ASSIGN, a program for exhaustive NMR chemical shift assignments of large proteins from complete or incomplete triple-resonance data. J Biomol NMR 57:179-91
Ragsdale, Stephen W; Yi, Li; Bender, Güne? et al. (2012) Redox, haem and CO in enzymatic catalysis and regulation. Biochem Soc Trans 40:501-7
Gupta, Nirupama; Ragsdale, Stephen W (2011) Thiol-disulfide redox dependence of heme binding and heme ligand switching in nuclear hormone receptor rev-erb{beta}. J Biol Chem 286:4392-403
Ragsdale, Stephen W; Yi, Li (2011) Thiol/Disulfide redox switches in the regulation of heme binding to proteins. Antioxid Redox Signal 14:1039-47
Bagai, Ireena; Ragsdale, Stephen W; Zuiderweg, Erik R P (2011) Pseudo-4D triple resonance experiments to resolve HN overlap in the backbone assignment of unfolded proteins. J Biomol NMR 49:69-74

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