1m8e
inducible nitric oxide synthase with 7-nitroindazole bound
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OverviewOverview
Nitric oxide is a key signaling molecule in many biological processes, making regulation of nitric oxide levels highly desirable for human, medicine and for advancing our understanding of basic physiology., Designing inhibitors to specifically target one of the three nitric oxide, synthase (NOS) isozymes that form nitric oxide from the L-Arg substrate, poses a significant challenge due to the overwhelmingly conserved active, sites. We report here 10 new X-ray crystallographic structures of, inducible and endothelial NOS oxygenase domains cocrystallized with, chlorzoxazone and four nitroindazoles: 5-nitroindazole, 6-nitroindazole, 7-nitroindazole, and 3-bromo-7-nitroindazole. Each of these bicyclic, aromatic inhibitors has only one hydrogen bond donor and therefore cannot, form the bidentate hydrogen bonds that the L-Arg substrate makes with, Glu371. Instead, all of these inhibitors induce a conformational change in, Glu371, creating an active site with altered molecular recognition, properties. The cost of this conformational change is approximately 1-2, kcal, based on our measured constants for inhibitor binding to the, wild-type and E371A mutant proteins. These inhibitors derive affinity by, pi-stacking above the heme and replacing both intramolecular, (Glu371-Met368) and intermolecular (substrate-Trp366) hydrogen bonds to, the beta-sheet architecture underlying the active site. When bound to NOS, high-affinity inhibitors in this class are planar, whereas weaker, inhibitors are nonplanar. Isozyme differences were observed in the pterin, cofactor site, the heme propionate, and inhibitor positions. Computational, docking predictions match the crystallographic results, including the, Glu371 conformational change and inhibitor-binding orientations, and, support a combined crystallographic and computational approach to, isozyme-specific NOS inhibitor analysis and design.
About this StructureAbout this Structure
1M8E is a Single protein structure of sequence from Mus musculus with HEM, H4B and 7NI as ligands. Active as Nitric-oxide synthase, with EC number 1.14.13.39 Full crystallographic information is available from OCA.
ReferenceReference
Conformational changes in nitric oxide synthases induced by chlorzoxazone and nitroindazoles: crystallographic and computational analyses of inhibitor potency., Rosenfeld RJ, Garcin ED, Panda K, Andersson G, Aberg A, Wallace AV, Morris GM, Olson AJ, Stuehr DJ, Tainer JA, Getzoff ED, Biochemistry. 2002 Nov 26;41(47):13915-25. PMID:12437348
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