title: Structure of nitric oxide synthase oxygenase dimer with pterin and substrate.
abstract: Crystal structures of the murine cytokine-inducible nitric oxide synthase oxygenase dimer with active-center water molecules, the substrate L-arginine (L-Arg), or product analog thiocitrulline reveal how dimerization, cofactor tetrahydrobiopterin, and L-Arg binding complete the catalytic center for synthesis of the essential biological signal and cytotoxin nitric oxide. Pterin binding refolds the central interface region, recruits new structural elements, creates a 30 angstrom deep active-center channel, and causes a 35 degrees helical tilt to expose a heme edge and the adjacent residue tryptophan-366 for likely reductase domain interactions and caveolin inhibition. Heme propionate interactions with pterin and L-Arg suggest that pterin has electronic influences on heme-bound oxygen. L-Arginine binds to glutamic acid-371 and stacks with heme in an otherwise hydrophobic pocket to aid activation of heme-bound oxygen by direct proton donation and thereby differentiate the two chemical steps of nitric oxide synthesis.
authors.affiliation: Department of Molecular Biology and Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
authors.forename: B R
authors.initials: BR
authors.lastname: Crane
authors.forename: A S
authors.initials: AS
authors.lastname: Arvai
authors.forename: D K
authors.initials: DK
authors.lastname: Ghosh
authors.forename: C
authors.initials: C
authors.lastname: Wu
authors.forename: E D
authors.initials: ED
authors.lastname: Getzoff
authors.forename: D J
authors.initials: DJ
authors.lastname: Stuehr
authors.forename: J A
authors.initials: JA
authors.lastname: Tainer
mesh_terms: D000818:Animals; D001120:Arginine / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D001708:Biopterins / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D002956:Citrulline / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D018360:Crystallography, X-Ray; D019281:Dimerization; D006860:Hydrogen Bonding; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism; D008024:Ligands; D008264:Macrophages / Q000201:enzymology; D051379:Mice; D008958:Models, Molecular; D009569:Nitric Oxide / Q000096:biosynthesis; D019001:Nitric Oxide Synthase / Q000737:chemistry* / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D013890:Thiourea / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism
chemical_list: D007527:Isoenzymes; D008024:Ligands; C086715:thiocitrulline; D001708:Biopterins; D002956:Citrulline; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; C003402:sapropterin; D013890:Thiourea