Structure of nitric oxide synthase oxygenase dimer with pterin and substrate.
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.
Crane
B R
BR
Department of Molecular Biology and Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
Arvai
A S
AS
Ghosh
D K
DK
Wu
C
C
Getzoff
E D
ED
Stuehr
D J
DJ
Tainer
J A
JA
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
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