title: Electron spin echo envelope modulation studies of the Cu(II)-substituted derivative of isopenicillin N synthase: a structural and spectroscopic model.
abstract: Electron spin echo envelope modulation spectroscopy (ESEEM) was used to study the active site structure of isopenicillin N synthase (IPNS) from Cephalosporium acremonium with Cu(II) as a spectroscopic probe. Fourier transform of the stimulated electron spin-echo envelope for the Cu(II)-substituted enzyme, Cu(II)IPNS, revealed two nearly magnetically equivalent, equatorially coordinated His imidazoles. The superhyperfine coupling constant, Aiso, for the remote 14N of each imidazole was 1.65 MHz. The binding of substrate to the enzyme altered the magnetic coupling so that Aiso is 1.30 MHz for one nitrogen and 2.16 MHz for the other. From a comparison of the ESEEM of Cu(II)IPNS in D2O and H2O, it is suggested that water is a ligand of Cu(II) and this is displaced upon the addition of substrate.
authors.affiliation: Department of Molecular Pharmacology, Albert Einstein College of Medicine, Yeshiva University, Bronx, New York 10461.
authors.forename: F
authors.initials: F
authors.lastname: Jiang
authors.forename: J
authors.initials: J
authors.lastname: Peisach
authors.forename: L J
authors.initials: LJ
authors.lastname: Ming
authors.forename: L
authors.initials: L
authors.lastname: Que
authors.forename: V J
authors.initials: VJ
authors.lastname: Chen
mesh_terms: D000164:Acremonium / Q000201:enzymology; D001665:Binding Sites; D003300:Copper / Q000737:chemistry* / Q000378:metabolism; D003903:Deuterium; D004578:Electron Spin Resonance Spectroscopy; D005583:Fourier Analysis; D006639:Histidine / Q000378:metabolism; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D009584:Nitrogen / Q000737:chemistry; D009842:Oligopeptides / Q000378:metabolism; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism; D014867:Water
chemical_list: D009842:Oligopeptides; D014867:Water; C011638:5-(2-aminoadipyl)cysteinylvaline; D006639:Histidine; D003300:Copper; D003903:Deuterium; D010088:Oxidoreductases; C038370:isopenicillin N synthetase; D009584:Nitrogen