title: Crystal structure of nitric oxide synthase bound to nitro indazole reveals a novel inactivation mechanism.
abstract: Nitric oxide is generated under normal and pathophysiological conditions by three distinct isoforms of nitric oxide synthase (NOS). A small-molecule inhibitor of NOS (3-Br-7-nitroindazole, 7-NIBr) is profoundly neuroprotective in mouse models of stroke and Parkinson's disease. We report the crystal structure of the catalytic heme domain of endothelial NOS complexed with 7-NIBr at 1.65 A resolution. Critical to the binding of 7-NIBr at the substrate site is the adoption by eNOS of an altered conformation, in which a key glutamate residue swings out toward one of the heme propionate groups. Perturbation of the heme propionate ensues and eliminates the cofactor tetrahydrobiopterin-heme interaction. We also present three crystal structures that reveal how alterations at the substrate site facilitate 7-NIBr and structurally dissimilar ligands to occupy the cofactor site.
authors.affiliation: Department of Molecular Biology & Biochemistry, University of California, Irvine, California 92697, USA. c.s.raman@uth.tmc.edu
authors.forename: C S
authors.initials: CS
authors.lastname: Raman
authors.forename: H
authors.initials: H
authors.lastname: Li
authors.forename: P
authors.initials: P
authors.lastname: Martásek
authors.forename: G
authors.initials: G
authors.lastname: Southan
authors.forename: B S
authors.initials: BS
authors.lastname: Masters
authors.forename: T L
authors.initials: TL
authors.lastname: Poulos
mesh_terms: D001665:Binding Sites; D001708:Biopterins / Q000031:analogs & derivatives* / Q000737:chemistry; D003460:Crystallization; D018360:Crystallography, X-Ray; D015195:Drug Design; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000494:pharmacology; D007191:Indazoles / Q000737:chemistry* / Q000494:pharmacology; D008958:Models, Molecular; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000737:chemistry*; D019335:Nitroarginine / Q000737:chemistry* / Q000494:pharmacology; D011487:Protein Conformation; D013379:Substrate Specificity
chemical_list: C106731:3-bromo-7-nitroindazole; D004791:Enzyme Inhibitors; D007191:Indazoles; D019335:Nitroarginine; D001708:Biopterins; D019001:Nitric Oxide Synthase; C003402:sapropterin