The overall Project goal is to understand how nitric oxide synthase (NOS) isozymes regulate the synthesis of nitric oxide (NO) and thereby its dual biological activities as (i) a diffusible messenger for neurotransmission, long-term potentiation, platelet aggregation and blood pressure regulation, and (ii) a cytotoxic agent for defense against tumor cells and parasites. The inducible (iNOS), endothelial (eNOS), and neuronal (nNOS) isoforms achieve their key functions via an intriguing calcium-regulated electron-transfer mechanism and a unique assembly of at least five cofactors. Each subunit of the NOS dimer has two modules joined by a calmodulin-binding (CaM) hinge region: 1) an oxygenase domain (NOSox) with heme, tetrahydrobiopterin (H4B), and L-Arg binding sites forming the catalytic center for NO production, plus a single structural Zn site at the dimer interface, and 2) a reductase module (NOSred) with NADPH, FAD, and FMN sites supplying electrons to the heme. Systematic characterizations of all three isozymes and individual NOSox, CaM-binding, and NOSred components will address the complex structural biochemistry underlying NOS activity, isozyme specificity, and regulation. Coupled Stuehr, Tamner, and Getzoff group efforts will insure efficient application of unified structure-function studies. Biochemical and mutational characterizations by the Stuehr group will proceed in concert with coupled experimental crystallographic, solution scattering and electron microscopic results plus computational structural analyses by the Getzoff and Tamner groups. As an integrated whole, this project will provide the basis to develop and test hypotheses, and to thereby bridge the growing gap between huge increases in detailed NOS structural and biochemical data and in-depth comprehension of NOS activities. This work focuses on defining conserved and variable isozyme features responsible for 1) catalytic activity and regulation of NOSox, 2) ligand binding to NOSox isozymes, 3) structure and activity of NOSred, and 4) domain interactions in assembled NOS. Designed NOS mutants will be used to experimentally test emerging principles for NOS structure and function. This coordinated structural biochemistry cycle aims to provide a molecular understanding of the activity, inhibition, and regulation of NOS isozymes relevant to important aspects of their biology. These results will furthermore build the essential framework for a unified understanding of NOS relevant to the design of structure-based inhibitors as desirable chemical tools for studying NOS function and as therapeutic agents for stroke, septic shock, and inflammatory damage.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL058883-08
Application #
6859368
Study Section
Physical Biochemistry Study Section (PB)
Program Officer
Lin, Michael
Project Start
1997-08-15
Project End
2007-01-31
Budget Start
2005-04-01
Budget End
2007-01-31
Support Year
8
Fiscal Year
2005
Total Cost
$473,660
Indirect Cost
Name
Scripps Research Institute
Department
Type
DUNS #
781613492
City
La Jolla
State
CA
Country
United States
Zip Code
92037
Haque, Mohammad Mahfuzul; Bayachou, Mekki; Fadlalla, Mohammed A et al. (2013) Charge-pairing interactions control the conformational setpoint and motions of the FMN domain in neuronal nitric oxide synthase. Biochem J 450:607-17
Haque, Mohammad Mahfuzul; Tejero, Jesús; Bayachou, Mekki et al. (2013) Thermodynamic characterization of five key kinetic parameters that define neuronal nitric oxide synthase catalysis. FEBS J 280:4439-53
Nagpal, Latika; Haque, Mohammad M; Saha, Amit et al. (2013) Mechanism of inducible nitric-oxide synthase dimerization inhibition by novel pyrimidine imidazoles. J Biol Chem 288:19685-97
Haque, Mohammad Mahfuzul; Fadlalla, Mohammed A; Aulak, Kulwant S et al. (2012) Control of electron transfer and catalysis in neuronal nitric-oxide synthase (nNOS) by a hinge connecting its FMN and FAD-NADPH domains. J Biol Chem 287:30105-16
Haque, Mohammad M; Kenney, Claire; Tejero, Jesús et al. (2011) A kinetic model linking protein conformational motions, interflavin electron transfer and electron flux through a dual-flavin enzyme-simulating the reductase activity of the endothelial and neuronal nitric oxide synthase flavoprotein domains. FEBS J 278:4055-69
Rosenfeld, Robin J; Bonaventura, Joseph; Szymczyna, Blair R et al. (2010) Nitric-oxide synthase forms N-NO-pterin and S-NO-cys: implications for activity, allostery, and regulation. J Biol Chem 285:31581-9
Guan, Zhi-Wen; Haque, Mohammad Mahfuzul; Wei, Chin-Chuan et al. (2010) Lys842 in neuronal nitric-oxide synthase enables the autoinhibitory insert to antagonize calmodulin binding, increase FMN shielding, and suppress interflavin electron transfer. J Biol Chem 285:3064-75
Haque, Mohammad Mahfuzul; Fadlalla, Mohammed; Wang, Zhi-Qiang et al. (2009) Neutralizing a surface charge on the FMN subdomain increases the activity of neuronal nitric-oxide synthase by enhancing the oxygen reactivity of the enzyme heme-nitric oxide complex. J Biol Chem 284:19237-47
Garcin, Elsa D; Arvai, Andrew S; Rosenfeld, Robin J et al. (2008) Anchored plasticity opens doors for selective inhibitor design in nitric oxide synthase. Nat Chem Biol 4:700-7
Wei, Chin-Chuan; Wang, Zhi-Qiang; Tejero, Jesus et al. (2008) Catalytic reduction of a tetrahydrobiopterin radical within nitric-oxide synthase. J Biol Chem 283:11734-42

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