title: Structural characterization of Zn(II)-, Co(II)-, and Mn(II)-loaded forms of the argE-encoded N-acetyl-L-ornithine deacetylase from Escherichia coli.
abstract: The Zn, Co, and Mn K-edge extended X-ray absorption fine structure (EXAFS) spectra of the N-acetyl-l-ornithine deacetylase (ArgE) from Escherichia coli, loaded with one or two equivalents of divalent metal ions (i.e., [Zn(II)_(ArgE)], [Zn(II)Zn(II)(ArgE)], [Co(II)_(ArgE)], [Co(II)Co(II)(ArgE)], [Mn(II)_(ArgE)], and [Mn(II)Mn(II)(ArgE)]), were recorded. The Fourier transformed data (FT) for [Zn(II)_(ArgE)], [Zn(II)Zn(II)(ArgE)], [Co(II)_(ArgE)] and [Co(II)Co(II)(ArgE)] are dominated by a peak at 2.05Å, that can be fit assuming five or six light atom (N,O) scatterers. Inclusion of multiple-scattering contributions from the outer-shell atoms of a histidine-imidazole ring resulted in reasonable Debye-Waller factors for these contributions and a slight reduction in the goodness-of-fit value (f'). Furthermore, the data best fit a model that included a M-M vector at 3.3 and 3.4Å for Zn(II) and Co(II), respectively, suggesting the formation of a dinuclear site. Multiple scattering contributions from the outer-shell atoms of a histidine-imidazole rings are observed at ~3 and 4Å for Zn(II)- and Co(II)-loaded ArgE suggesting at least one histidine ligand at each metal binding site. Likewise, EXAFS data for Mn(II)-loaded ArgE are dominated by a peak at 2.19Å that was best fit assuming six light atom (N,O) scatterers. Due to poor signal to noise ratios for the Mn EXAFS spectra, no Mn-Mn vector could be modeled. Peak intensities for [M(II)_(ArgE)] vs. [M(II)M(II)(ArgE)] suggest the Zn(II), Co(II), and Mn(II) bind to ArgE in a cooperative manner. Since no structural data has been reported for any ArgE enzyme, the EXAFS data reported herein represent the first structural glimpse for ArgE enzymes. These data also provide a structural foundation for the future design of small molecules that function as inhibitors of ArgE and may potentially function as a new class of antibiotics.
authors.affiliation: Department of Chemistry and Biochemistry & Molecular Biology, University of Georgia, Athens, GA 30602-2556, USA.
authors.forename: Ye
authors.initials: Y
authors.lastname: Tao
authors.forename: Jacob E
authors.initials: JE
authors.lastname: Shokes
authors.forename: Wade C
authors.initials: WC
authors.lastname: McGregor
authors.forename: Robert A
authors.initials: RA
authors.lastname: Scott
authors.forename: Richard C
authors.initials: RC
authors.lastname: Holz
mesh_terms: D000581:Amidohydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001120:Arginine / Q000737:chemistry / Q000378:metabolism; D002413:Cations, Divalent; D003035:Cobalt / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008345:Manganese / Q000737:chemistry* / Q000378:metabolism; D008667:Metalloproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008956:Models, Chemical; D015394:Molecular Structure; D011073:Polyamines / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D056928:X-Ray Absorption Spectroscopy / Q000379:methods; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism
chemical_list: D002413:Cations, Divalent; D029968:Escherichia coli Proteins; D008667:Metalloproteins; D011073:Polyamines; D003035:Cobalt; D008345:Manganese; D001120:Arginine; D000581:Amidohydrolases; C018732:N-acetylornithine deacetylase; D015032:Zinc