title: Electron paramagnetic resonance spectroscopy of the heme domain of inducible nitric oxide synthase: binding of ligands at the arginine site induces changes in the heme ligation geometry.
abstract: The electron paramagnetic resonance spectra of the heme domain of inducible nitric oxide synthase (iNOS) demonstrate a close relationship to the corresponding spectra of the neuronal isoform (nNOS). The binding of ligands to the iNOS arginine site perturbs the environment of the high-spin ferriheme in a highly ligand-specific manner. The iNOS forms five-coordinate, high-spin complexes with arginine analogs which are clearly related to the corresponding complexes of nNOS. Studies indicate that the binding of L-arginine, N(omega)-hydroxy-L-arginine (NHA), and N(omega)-methyl-L-arginine (NMA) produces various spectroscopic species closely corresponding to the equivalent complexes of nNOS, while N(omega)-nitro-L-arginine (NNA) binding produces a state which appears intermediate in character between the nNOS NNA and arginine complexes. These spectroscopic studies have permitted the determination of ligand-specific high-spin states which reveal similarities and differences between iNOS and nNOS.
authors.affiliation: Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Salerno
authors.forename: P
authors.initials: P
authors.lastname: Martasek
authors.forename: L J
authors.initials: LJ
authors.lastname: Roman
authors.forename: B S
authors.initials: BS
authors.lastname: Masters
mesh_terms: D000818:Animals; D001120:Arginine; D001483:Base Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D017931:DNA Primers; D004578:Electron Spin Resonance Spectroscopy; D006418:Heme / Q000378:metabolism; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism; D008024:Ligands; D051379:Mice; D008969:Molecular Sequence Data; D019001:Nitric Oxide Synthase / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000302:isolation & purification; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D017931:DNA Primers; D007527:Isoenzymes; D008024:Ligands; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D006418:Heme; D001120:Arginine; D019001:Nitric Oxide Synthase