title: Structure-based design and synthesis of N(omega)-nitro-L-arginine-containing peptidomimetics as selective inhibitors of neuronal nitric oxide synthase. Displacement of the heme structural water.
abstract: The neuronal isoform of nitric oxide synthase (nNOS), the enzyme responsible for the production of nitric oxide in the central nervous system, represents an attractive target for the treatment of various neurodegenerative disorders. X-ray crystal structures of complexes of nNOS with two nNOS-selective inhibitors, (4S)-N-{4-amino-5-[(2-aminoethylamino]pentyl}-N'-nitroguanidine (1) and 4-N-(Nomega-nitro-l-argininyl)-trans-4-amino-l-proline amide (2), led to the discovery of a conserved structural water molecule that was hydrogen bonded between the two heme propionates and the inhibitors (Figure 2). On the basis of this observation, we hypothesized that by attaching a hydrogen bond donor group to the amide nitrogen of 2 or to the secondary amine nitrogen of 1, the inhibitor molecules could displace the structural water molecule and obtain a direct interaction with the heme cofactor. To test this hypothesis, peptidomimetic analogues 3-5, which have either an N-hydroxyl (3 and 5) or N-amino (4) donor group, were designed and synthesized. X-ray crystal structures of nNOS with inhibitors 3 and 5 bound verified that the N-hydroxyl group had, indeed, displaced the structural water molecule and provided a direct interaction with the heme propionate moiety (Figures 5 and 6). Surprisingly, in vitro activity assay results indicated that the addition of a hydroxyl group (3) only increased the potency slightly against the neuronal isoform over the parent compound (1). Rationalizations for the small increase in potency are consistent with other changes in the crystal structures.
authors.affiliation: Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, USA.
authors.forename: Jiwon
authors.initials: J
authors.lastname: Seo
authors.forename: Jotato
authors.initials: J
authors.lastname: Igarashi
authors.forename: Huiying
authors.initials: H
authors.lastname: Li
authors.forename: Pavel
authors.initials: P
authors.lastname: Martasek
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Roman
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Poulos
authors.forename: Richard B
authors.initials: RB
authors.lastname: Silverman
mesh_terms: D032701:Biomimetics; D018360:Crystallography, X-Ray; D015195:Drug Design; D006418:Heme / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D015394:Molecular Structure; D052248:Nitric Oxide Synthase Type I / Q000037:antagonists & inhibitors* / Q000737:chemistry*; D019335:Nitroarginine / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000737:chemistry; D010455:Peptides / Q000737:chemistry*; D020033:Protein Isoforms / Q000037:antagonists & inhibitors / Q000737:chemistry; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D010455:Peptides; D020033:Protein Isoforms; D014867:Water; D019335:Nitroarginine; D006418:Heme; D052248:Nitric Oxide Synthase Type I