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Spectroscopic and Computational Studies of Ni Superoxide Dismutase: Electronic Structure Contributions to Enzymatic Function.

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Title: Spectroscopic and Computational Studies of Ni Superoxide Dismutase: Electronic Structure Contributions to Enzymatic Function.
Authors: Fiedler, Adam T.1, Bryngelson, Peter A.2, Maroney, Michael J.2, Brunold, Thomas C.1 brunold@chem.wisc.edu
Source: Journal of the American Chemical Society. 4/20/2005, Vol. 127 Issue 15, p5449-5462. 14p.
Subjects: Superoxide dismutase, Manganese enzymes, Electronic structure, Metalloenzymes, Metalloproteins, Molecular spectroscopy, Absorption spectra
Abstract: Ni-containing superoxide dismutase (NiSOD) is the most recently discovered member of the class of metalloenzymes that detoxify the superoxide radical in aerobic organisms. In this study, we have employed a variety of spectroscopic and computational methods to probe the electronic structure of the NiSOD active site in both its oxidized (NiSODox, possessing a low-spin (S = ½) Ni3+ center) and reduced (NiSODred, containing a diamagnetic Ni2+ center) states. Our experimentally validated computed electronic-structure description for NiSODox reveals strong σ-bonding interactions between Ni and the equatorial S/N ligands, which give rise to intense charge-transfer transitions in the near-UV region of the absorption spectrum. Resonance Raman (rR) spectra obtained with laser excitation in this region exhibit two features at 349 and 365 cm-1 that are assigned to Ni-SCys stretching modes. The NiSODred active site also exhibits a high degree of metal-ligand bond covalency as well as filled/filled π-interactions between Ni and S/N orbitals, which serve to adjust the redox potential of the Ni2+ center. Comparison of our computational results for NiSODred with those obtained in parallel studies of synthetic [NiS2N2] complexes reveals that the presence of an anionic N-donor ligand is crucial for promoting metal-based (versus S-based) oxidation of the active site. The implications of our electronic-structure descriptions with respect to the function of NiSOD are discussed, and a comparison of M-SCys bonding in NiSOD and other metalloenzymes with sulfur ligation is provided. [ABSTRACT FROM AUTHOR]
Copyright of Journal of the American Chemical Society is the property of American Chemical Society and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: Spectroscopic and Computational Studies of Ni Superoxide Dismutase: Electronic Structure Contributions to Enzymatic Function.
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  Data: <searchLink fieldCode="AR" term="%22Fiedler%2C+Adam+T%2E%22">Fiedler, Adam T.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Bryngelson%2C+Peter+A%2E%22">Bryngelson, Peter A.</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22Maroney%2C+Michael+J%2E%22">Maroney, Michael J.</searchLink><relatesTo>2</relatesTo><br /><searchLink fieldCode="AR" term="%22Brunold%2C+Thomas+C%2E%22">Brunold, Thomas C.</searchLink><relatesTo>1</relatesTo><i> brunold@chem.wisc.edu</i>
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  Data: <searchLink fieldCode="JN" term="%22Journal+of+the+American+Chemical+Society%22">Journal of the American Chemical Society</searchLink>. 4/20/2005, Vol. 127 Issue 15, p5449-5462. 14p.
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  Data: <searchLink fieldCode="DE" term="%22Superoxide+dismutase%22">Superoxide dismutase</searchLink><br /><searchLink fieldCode="DE" term="%22Manganese+enzymes%22">Manganese enzymes</searchLink><br /><searchLink fieldCode="DE" term="%22Electronic+structure%22">Electronic structure</searchLink><br /><searchLink fieldCode="DE" term="%22Metalloenzymes%22">Metalloenzymes</searchLink><br /><searchLink fieldCode="DE" term="%22Metalloproteins%22">Metalloproteins</searchLink><br /><searchLink fieldCode="DE" term="%22Molecular+spectroscopy%22">Molecular spectroscopy</searchLink><br /><searchLink fieldCode="DE" term="%22Absorption+spectra%22">Absorption spectra</searchLink>
– Name: Abstract
  Label: Abstract
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  Data: Ni-containing superoxide dismutase (NiSOD) is the most recently discovered member of the class of metalloenzymes that detoxify the superoxide radical in aerobic organisms. In this study, we have employed a variety of spectroscopic and computational methods to probe the electronic structure of the NiSOD active site in both its oxidized (NiSODox, possessing a low-spin (S = ½) Ni3+ center) and reduced (NiSODred, containing a diamagnetic Ni2+ center) states. Our experimentally validated computed electronic-structure description for NiSODox reveals strong σ-bonding interactions between Ni and the equatorial S/N ligands, which give rise to intense charge-transfer transitions in the near-UV region of the absorption spectrum. Resonance Raman (rR) spectra obtained with laser excitation in this region exhibit two features at 349 and 365 cm-1 that are assigned to Ni-SCys stretching modes. The NiSODred active site also exhibits a high degree of metal-ligand bond covalency as well as filled/filled π-interactions between Ni and S/N orbitals, which serve to adjust the redox potential of the Ni2+ center. Comparison of our computational results for NiSODred with those obtained in parallel studies of synthetic [NiS2N2] complexes reveals that the presence of an anionic N-donor ligand is crucial for promoting metal-based (versus S-based) oxidation of the active site. The implications of our electronic-structure descriptions with respect to the function of NiSOD are discussed, and a comparison of M-SCys bonding in NiSOD and other metalloenzymes with sulfur ligation is provided. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
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  Data: <i>Copyright of Journal of the American Chemical Society is the property of American Chemical Society and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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        Value: 10.1021/ja042521i
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      – Code: eng
        Text: English
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        PageCount: 14
        StartPage: 5449
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      – SubjectFull: Superoxide dismutase
        Type: general
      – SubjectFull: Manganese enzymes
        Type: general
      – SubjectFull: Electronic structure
        Type: general
      – SubjectFull: Metalloenzymes
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      – SubjectFull: Metalloproteins
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      – SubjectFull: Molecular spectroscopy
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      – SubjectFull: Absorption spectra
        Type: general
    Titles:
      – TitleFull: Spectroscopic and Computational Studies of Ni Superoxide Dismutase: Electronic Structure Contributions to Enzymatic Function.
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            NameFull: Fiedler, Adam T.
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            NameFull: Bryngelson, Peter A.
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            NameFull: Maroney, Michael J.
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            NameFull: Brunold, Thomas C.
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              Text: 4/20/2005
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              Y: 2005
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