Anion binding to bovine erythrocyte superoxide dismutase studied by X-ray absorption spectroscopy. A detailed structural analysis of the native enzyme and the azido and cyano derivatives using a multiple-scattering approach

Ninian Blackburn, Richard W. Strange, Loretta M. McFadden, S. Samar Hasnain

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Abstract

X-ray absorption spectra are reported for the native, azide-bound, and cyanide-bound forms of bovine erythrocyte superoxide dismutase (SOD). Absorption edge data suggest a similar geometric structure for the native enzyme and the azido derivative, but a different coordination structure for the cyano derivative. Analysis of the EXAFS, using a recently developed multiple-scattering method for treating systems containing metal-histidine coordination, has allowed accurate simulation of the raw unfiltered EXAFS data over the range k = 3-13 Å-1. The analysis has provided structural details of the coordinated imidazole rings in addition to structural parameters for the coordinated anions. Thus azide is coordinated in an equatorial position of a square-pyramidal site, with Cu-N(azide) = 1.99 Å and a Cu-N-N angle of less than ca. 135°. The cyanide group is also coordinated in an equatorial position, with Cu-C = 1.97 Å and a Cu-C-N angle of 180°. The multiple-scattering analysis of the linear Cu-C-N group has allowed determination of the C-N distance of the cyano group as 1.18 Å. Unlike azido-SOD, which retains an axial imidazole group at 2.27 Å, the cyano derivative appears to be 4-coordinate, with no evidence for an additional coordinated histidine. Detailed analysis of the outer-shell contributions from the coordinated histidine groups indicates that the imidazole rings are asymmetrically coordinated, with the degree of asymmetry depending on the identity of the derivative. It is suggested that the latter effect results from alteration in Nδ-H-bonding interactions of the coordinated imidazoles with the polypeptide chain.

Original languageEnglish (US)
Pages (from-to)7162-7170
Number of pages9
JournalJournal of the American Chemical Society
Volume109
Issue number23
StatePublished - 1987
Externally publishedYes

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X-Ray Absorption Spectroscopy
X ray absorption spectroscopy
Azides
Multiple scattering
Histidine
Structural analysis
Superoxide Dismutase
Anions
Negative ions
Enzymes
Erythrocytes
Cyanides
Derivatives
Imidazoles
Polypeptides
X ray absorption
Metals
X-Rays
Absorption spectra
Peptides

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

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title = "Anion binding to bovine erythrocyte superoxide dismutase studied by X-ray absorption spectroscopy. A detailed structural analysis of the native enzyme and the azido and cyano derivatives using a multiple-scattering approach",
abstract = "X-ray absorption spectra are reported for the native, azide-bound, and cyanide-bound forms of bovine erythrocyte superoxide dismutase (SOD). Absorption edge data suggest a similar geometric structure for the native enzyme and the azido derivative, but a different coordination structure for the cyano derivative. Analysis of the EXAFS, using a recently developed multiple-scattering method for treating systems containing metal-histidine coordination, has allowed accurate simulation of the raw unfiltered EXAFS data over the range k = 3-13 {\AA}-1. The analysis has provided structural details of the coordinated imidazole rings in addition to structural parameters for the coordinated anions. Thus azide is coordinated in an equatorial position of a square-pyramidal site, with Cu-N(azide) = 1.99 {\AA} and a Cu-N-N angle of less than ca. 135°. The cyanide group is also coordinated in an equatorial position, with Cu-C = 1.97 {\AA} and a Cu-C-N angle of 180°. The multiple-scattering analysis of the linear Cu-C-N group has allowed determination of the C-N distance of the cyano group as 1.18 {\AA}. Unlike azido-SOD, which retains an axial imidazole group at 2.27 {\AA}, the cyano derivative appears to be 4-coordinate, with no evidence for an additional coordinated histidine. Detailed analysis of the outer-shell contributions from the coordinated histidine groups indicates that the imidazole rings are asymmetrically coordinated, with the degree of asymmetry depending on the identity of the derivative. It is suggested that the latter effect results from alteration in Nδ-H-bonding interactions of the coordinated imidazoles with the polypeptide chain.",
author = "Ninian Blackburn and Strange, {Richard W.} and McFadden, {Loretta M.} and Hasnain, {S. Samar}",
year = "1987",
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T1 - Anion binding to bovine erythrocyte superoxide dismutase studied by X-ray absorption spectroscopy. A detailed structural analysis of the native enzyme and the azido and cyano derivatives using a multiple-scattering approach

AU - Blackburn, Ninian

AU - Strange, Richard W.

AU - McFadden, Loretta M.

AU - Hasnain, S. Samar

PY - 1987

Y1 - 1987

N2 - X-ray absorption spectra are reported for the native, azide-bound, and cyanide-bound forms of bovine erythrocyte superoxide dismutase (SOD). Absorption edge data suggest a similar geometric structure for the native enzyme and the azido derivative, but a different coordination structure for the cyano derivative. Analysis of the EXAFS, using a recently developed multiple-scattering method for treating systems containing metal-histidine coordination, has allowed accurate simulation of the raw unfiltered EXAFS data over the range k = 3-13 Å-1. The analysis has provided structural details of the coordinated imidazole rings in addition to structural parameters for the coordinated anions. Thus azide is coordinated in an equatorial position of a square-pyramidal site, with Cu-N(azide) = 1.99 Å and a Cu-N-N angle of less than ca. 135°. The cyanide group is also coordinated in an equatorial position, with Cu-C = 1.97 Å and a Cu-C-N angle of 180°. The multiple-scattering analysis of the linear Cu-C-N group has allowed determination of the C-N distance of the cyano group as 1.18 Å. Unlike azido-SOD, which retains an axial imidazole group at 2.27 Å, the cyano derivative appears to be 4-coordinate, with no evidence for an additional coordinated histidine. Detailed analysis of the outer-shell contributions from the coordinated histidine groups indicates that the imidazole rings are asymmetrically coordinated, with the degree of asymmetry depending on the identity of the derivative. It is suggested that the latter effect results from alteration in Nδ-H-bonding interactions of the coordinated imidazoles with the polypeptide chain.

AB - X-ray absorption spectra are reported for the native, azide-bound, and cyanide-bound forms of bovine erythrocyte superoxide dismutase (SOD). Absorption edge data suggest a similar geometric structure for the native enzyme and the azido derivative, but a different coordination structure for the cyano derivative. Analysis of the EXAFS, using a recently developed multiple-scattering method for treating systems containing metal-histidine coordination, has allowed accurate simulation of the raw unfiltered EXAFS data over the range k = 3-13 Å-1. The analysis has provided structural details of the coordinated imidazole rings in addition to structural parameters for the coordinated anions. Thus azide is coordinated in an equatorial position of a square-pyramidal site, with Cu-N(azide) = 1.99 Å and a Cu-N-N angle of less than ca. 135°. The cyanide group is also coordinated in an equatorial position, with Cu-C = 1.97 Å and a Cu-C-N angle of 180°. The multiple-scattering analysis of the linear Cu-C-N group has allowed determination of the C-N distance of the cyano group as 1.18 Å. Unlike azido-SOD, which retains an axial imidazole group at 2.27 Å, the cyano derivative appears to be 4-coordinate, with no evidence for an additional coordinated histidine. Detailed analysis of the outer-shell contributions from the coordinated histidine groups indicates that the imidazole rings are asymmetrically coordinated, with the degree of asymmetry depending on the identity of the derivative. It is suggested that the latter effect results from alteration in Nδ-H-bonding interactions of the coordinated imidazoles with the polypeptide chain.

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