title: Elucidating nitric oxide synthase domain interactions by molecular dynamics.
abstract: Nitric oxide synthase (NOS) is a multidomain enzyme that catalyzes the production of nitric oxide (NO) by oxidizing L-Arg to NO and L-citrulline. NO production requires multiple interdomain electron transfer steps between the flavin mononucleotide (FMN) and heme domain. Specifically, NADPH-derived electrons are transferred to the heme-containing oxygenase domain via the flavin adenine dinucleotide (FAD) and FMN containing reductase domains. While crystal structures are available for both the reductase and oxygenase domains of NOS, to date there is no atomic level structural information on domain interactions required for the final FMN-to-heme electron transfer step. Here, we evaluate a model of this final electron transfer step for the heme-FMN-calmodulin NOS complex based on the recent biophysical studies using a 105-ns molecular dynamics trajectory. The resulting equilibrated complex structure is very stable and provides a detailed prediction of interdomain contacts required for stabilizing the NOS output state. The resulting equilibrated complex model agrees well with previous experimental work and provides a detailed working model of the final NOS electron transfer step required for NO biosynthesis.
authors.affiliation: Department of Molecular Biology and Biochemistry, University of California, Irvine, California, 92697.|Department of Chemistry, University of California, Irvine, California, 92697.|Department of Pharmaceutical Sciences, University of California, Irvine, California, 92697.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Hollingsworth
authors.affiliation: Department of Molecular Biology and Biochemistry, University of California, Irvine, California, 92697.|Department of Chemistry, University of California, Irvine, California, 92697.|Department of Pharmaceutical Sciences, University of California, Irvine, California, 92697.
authors.forename: Jeffrey K
authors.initials: JK
authors.lastname: Holden
authors.affiliation: Department of Molecular Biology and Biochemistry, University of California, Irvine, California, 92697.|Department of Chemistry, University of California, Irvine, California, 92697.|Department of Pharmaceutical Sciences, University of California, Irvine, California, 92697.
authors.forename: Huiying
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Molecular Biology and Biochemistry, University of California, Irvine, California, 92697.|Department of Chemistry, University of California, Irvine, California, 92697.|Department of Pharmaceutical Sciences, University of California, Irvine, California, 92697.
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Poulos
mesh_terms: D002147:Calmodulin / Q000378:metabolism; D004579:Electron Transport; D005486:Flavin Mononucleotide / Q000378:metabolism; D006418:Heme / Q000378:metabolism; D006801:Humans; D056004:Molecular Dynamics Simulation; D009249:NADP / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000737:chemistry* / Q000378:metabolism*; D010084:Oxidation-Reduction; D054730:Protein Interaction Domains and Motifs
chemical_list: D002147:Calmodulin; D009569:Nitric Oxide; D006418:Heme; D009249:NADP; D005486:Flavin Mononucleotide; C496319:NOS2 protein, human; D052247:Nitric Oxide Synthase Type II
keywords: electron transfer; molecular dynamics; nitric oxide synthase; protein complex; redox partners