title: Structures of the neuronal and endothelial nitric oxide synthase heme domain with D-nitroarginine-containing dipeptide inhibitors bound.
abstract: In a continuing effort to unravel the structural basis for isoform-selective inhibition of nitric oxide synthase (NOS) by various inhibitors, we have determined the crystal structures of the nNOS and eNOS heme domain bound with two D-nitroarginine-containing dipeptide inhibitors, D-Lys-D-Arg(NO)2-NH(2) and D-Phe-D-Arg(NO)2-NH(2). These two dipeptide inhibitors exhibit similar binding modes in the two constitutive NOS isozymes, which is consistent with the similar binding affinities for the two isoforms as determined by K(i) measurements. The D-nitroarginine-containing dipeptide inhibitors are not distinguished by the amino acid difference between nNOS and eNOS (Asp 597 and Asn 368, respectively) which is key in controlling isoform selection for nNOS over eNOS observed for the L-nitroarginine-containing dipeptide inhibitors reported previously [Flinspach, M., et al. (2004) Nat. Struct. Mol. Biol. 11, 54-59]. The lack of a free alpha-amino group on the D-nitroarginine moiety makes the dipeptide inhibitor steer away from the amino acid binding pocket near the active site. This allows the inhibitor to extend into the solvent-accessible channel farther away from the active site, which enables the inhibitors to explore new isoform-specific enzyme-inhibitor interactions. This might be the structural basis for why these D-nitroarginine-containing inhibitors are selective for nNOS (or eNOS) over iNOS.
authors.affiliation: Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697-3900, USA.
authors.forename: Mack
authors.initials: M
authors.lastname: Flinspach
authors.forename: Huiying
authors.initials: H
authors.lastname: Li
authors.forename: Joumana
authors.initials: J
authors.lastname: Jamal
authors.forename: Weiping
authors.initials: W
authors.lastname: Yang
authors.forename: Hui
authors.initials: H
authors.lastname: Huang
authors.forename: Richard B
authors.initials: RB
authors.lastname: Silverman
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Poulos
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D002417:Cattle; D004151:Dipeptides / Q000737:chemistry* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000378:metabolism; D006418:Heme / Q000737:chemistry*; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000737:chemistry; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000378:metabolism; D052248:Nitric Oxide Synthase Type I; D052250:Nitric Oxide Synthase Type III; D019335:Nitroarginine / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats
chemical_list: D004151:Dipeptides; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D019335:Nitroarginine; D006418:Heme; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D052250:Nitric Oxide Synthase Type III; C496322:Nos1 protein, rat; C496316:Nos3 protein, rat