title: Importance of valine 567 in substrate recognition and oxidation by neuronal nitric oxide synthase.
abstract: Nitric oxide (NO) is synthesised by a two-step oxidation of -arginine (L-Arg) in the active site of nitric oxide synthase (NOS) with formation of an intermediate, N omega-hydroxy-L-Arg (NOHA). Crystal structures of NOSs have shown the importance of an active-site Val567 residue (numbered for rat neuronal NOS, nNOS) interacting with non-amino acid substrates. To investigate the role of this Val residue in substrate recognition and NO-formation activity by nNOS, we generated and purified four Val567 mutants of nNOS, Val567Leu, Val567Phe, Val567Arg and Val567Glu. We characterized these proteins and tested their ability to generate NO from the oxidation of natural substrates L-Arg and NOHA, and from N-hydroxyguanidines previously identified as alternative substrates for nNOS. The Val567Leu mutant displayed lower NO formation activities than the wild type (WT) in the presence of all tested compounds. Surprisingly, the Val567Phe mutant formed low amounts of NO only from NOHA. These two mutants displayed lower affinity for L-Arg and NOHA than the WT protein. Val576Glu and Val567Arg mutants were much less stable and did not lead to any formation of NO. These results suggest that Val567 is an important residue for preserving the integrity of the active site, for substrate binding, and subsequently for NO-formation in nNOS.
authors.affiliation: UMR 8601 CNRS, Université Paris V R. Descartes, 45 Rue des Saints-Pères, 75270 Paris Cedex 06, France.
authors.forename: Magali
authors.initials: M
authors.lastname: Moreau
authors.forename: Hiroto
authors.initials: H
authors.lastname: Takahashi
authors.forename: Marie-Agnes
authors.initials: MA
authors.lastname: Sari
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Boucher
authors.forename: Ikuko
authors.initials: I
authors.lastname: Sagami
authors.forename: Toru
authors.initials: T
authors.lastname: Shimizu
authors.forename: Daniel
authors.initials: D
authors.lastname: Mansuy
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics*; D000818:Animals; D001120:Arginine / Q000737:chemistry; D001665:Binding Sites / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics; D009569:Nitric Oxide / Q000737:chemistry; D019001:Nitric Oxide Synthase / Q000737:chemistry* / Q000235:genetics; D052248:Nitric Oxide Synthase Type I; D017354:Point Mutation / Q000235:genetics*; D017434:Protein Structure, Tertiary; D051381:Rats; D013379:Substrate Specificity / Q000235:genetics; D014633:Valine / Q000737:chemistry* / Q000235:genetics
chemical_list: D009419:Nerve Tissue Proteins; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat; D014633:Valine