title: An X-ray diffraction and X-ray absorption spectroscopy joint study of neuroglobin.
abstract: Neuroglobin (Ngb) is a member of the globin family expressed in the vertebrate brain, involved in neuroprotection. A combined approach of X-ray diffraction (XRD) on single crystal and X-ray absorption spectroscopy (XAS) in solution, allows to determine the oxidation state and the structure of the Fe-heme both in the bis-histidine and the CO-bound (NgbCO) states. The overall data demonstrate that under X-ray the iron is photoreduced fairly rapidly, and that the previously reported X-ray structure of ferric Ngb [B. Vallone, K. Nienhaus, M. Brunori, G.U. Nienhaus, Proteins 56 (2004) 85-92] very likely refers to a photoreduced species indistinguishable from the dithionite reduced protein. Results from the XAS analysis of NgbCO in solution are in good agreement with XRD data on the crystal. However prolonged X-ray exposure at 15K determines CO release. This preliminary result paves the way to experiments aimed at the characterization of pentacoordinate ferrous Ngb, the only species competent in binding external ligands such as O2, CO or NO.
authors.affiliation: Istituto di Biochimica e Biochimica Clinica, Università Cattolica del Sacro Cuore, Largo F. Vito 1, 00167 Rome, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Arcovito
authors.forename: Tommaso
authors.initials: T
authors.lastname: Moschetti
authors.forename: Paola
authors.initials: P
authors.lastname: D'Angelo
authors.forename: Giordano
authors.initials: G
authors.lastname: Mancini
authors.forename: Beatrice
authors.initials: B
authors.lastname: Vallone
authors.forename: Maurizio
authors.initials: M
authors.lastname: Brunori
authors.forename: Stefano
authors.initials: S
authors.lastname: Della Longa
mesh_terms: D000818:Animals; D002248:Carbon Monoxide / Q000737:chemistry; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D005914:Globins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006418:Heme / Q000737:chemistry; D006639:Histidine / Q000737:chemistry; D007501:Iron / Q000737:chemistry; D051379:Mice; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000078787:Neuroglobin; D010084:Oxidation-Reduction; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D013057:Spectrum Analysis / Q000379:methods; D014961:X-Ray Diffraction / Q000379:methods; D014965:X-Rays
chemical_list: D009419:Nerve Tissue Proteins; D000078787:Neuroglobin; D011994:Recombinant Proteins; D006418:Heme; D006639:Histidine; D002248:Carbon Monoxide; D005914:Globins; D007501:Iron