2HX3

Rat nNOS heme domain complexed with (4S)-N-{4-Amino-5-[(2-aminoethyl)-hydroxyamino]-pentyl}-N'-nitroguanidine

Summary for 2HX3

• Entry DOI: 10.2210/pdb2hx3/pdb
• Related: 1P6I 2HX2 2HX4
• Descriptor: Nitric-oxide synthase, ACETATE ION, ZINC ION, ... (7 entities in total)
• Functional Keywords: nitric oxide synthase, heme enzyme, inhibitor, oxidoreductase
• Biological source: Rattus norvegicus (Norway rat)
• Cellular location: Cell membrane, sarcolemma; Peripheral membrane protein (By similarity): P29476
• Total number of polymer chains: 2
• Total formula weight: 100050.61

Authors

Igarashi, J.,Li, H.,Poulos, T.L. (deposition date: 2006-08-02, release date: 2007-04-24, Last modification date: 2024-02-14)

Primary citation

Seo, J.,Igarashi, J.,Li, H.,Martasek, P.,Roman, L.J.,Poulos, T.L.,Silverman, R.B.
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.
J.Med.Chem., 50:2089-2099, 2007

PubMed 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.

PubMed: 17425297
DOI: 10.1021/jm061305c

Experimental method

X-RAY DIFFRACTION (2 Å)