Is there a bridging ligand in metal-substituted zinc β-lactamases? A spectroscopic and theoretical answer

The spectral features of Co(II)-substituted metallo-β-lactamases were analyzed. Nuclear magnetic resonance (NMR) evidence is provided that shows no magnetic coupling between the two metal ions in Co(II),Co(II)-βLII (β-lactamase II from Bacillus cereus), suggesting that no bridging ligand connects th...

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Detalles Bibliográficos
Publicado: 2002
Materias:
Co(II)
Electronic spectra
Metallo-β-lactamase
NMR
Theoretical calculation
Bridging ligands
Band structure
Charge transfer
Electronic structure
Enzymes
Nuclear magnetic resonance
Positive ions
Spectrum analysis
Ultraviolet spectroscopy
Zinc compounds
Quantum theory
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00207608_v88_n1_p118_Estiu
http://hdl.handle.net/20.500.12110/paper_00207608_v88_n1_p118_Estiu
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id paper:paper_00207608_v88_n1_p118_Estiu
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spelling paper:paper_00207608_v88_n1_p118_Estiu2023-06-08T14:41:44Z Is there a bridging ligand in metal-substituted zinc β-lactamases? A spectroscopic and theoretical answer Co(II) Electronic spectra Metallo-β-lactamase NMR Theoretical calculation Bridging ligands Band structure Charge transfer Electronic structure Enzymes Nuclear magnetic resonance Positive ions Spectrum analysis Ultraviolet spectroscopy Zinc compounds Quantum theory The spectral features of Co(II)-substituted metallo-β-lactamases were analyzed. Nuclear magnetic resonance (NMR) evidence is provided that shows no magnetic coupling between the two metal ions in Co(II),Co(II)-βLII (β-lactamase II from Bacillus cereus), suggesting that no bridging ligand connects them. Ultraviolet-visible (UV-vis) data are rationalized on the basis of semiempirical quantum chemical calculations of the intermediate neglect of differential overlap type (ZINDO/S). The binuclear active sites of the enzymes from B. cereus (βLII) and B. fragilis (CcrA) were modeled from the protein data bank (PDB) coordinates, and calculations were performed at the multireference configuration interaction level. The active site geometries of these enzymes were examined using the experimental electronic spectra as a guide. The model which best fits to the spectroscopic data lacks a bridging solvent molecule, in agreement with the NMR data. The model could also reproduce spectral changes seen in the mixed Zn(II),Co(II) adduct. The bands in the visible range are associated with ligand field transitions at the high-affinity site, whereas the UV-calculated features originate in ligand-to-metal charge transfer to the open shell Co(II) in the low-affinity site. These results indirectly support the hypothesis that the Co(II),Co(II) derivative of CcrA is also unbridged, in contrast with the structure of the native zinc enzyme. These results indicate that the existence of a bridging ligand is not necessary for metallo-β-lactamase activity, and that the second zinc ion is not essential for lowering the pK a of the bound water. © 2002 Wiley Periodicals, Inc. Int. J. Quantum Chem. 2002 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00207608_v88_n1_p118_Estiu http://hdl.handle.net/20.500.12110/paper_00207608_v88_n1_p118_Estiu
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Co(II)
Electronic spectra
Metallo-β-lactamase
NMR
Theoretical calculation
Bridging ligands
Band structure
Charge transfer
Electronic structure
Enzymes
Nuclear magnetic resonance
Positive ions
Spectrum analysis
Ultraviolet spectroscopy
Zinc compounds
Quantum theory
spellingShingle Co(II)
Electronic spectra
Metallo-β-lactamase
NMR
Theoretical calculation
Bridging ligands
Band structure
Charge transfer
Electronic structure
Enzymes
Nuclear magnetic resonance
Positive ions
Spectrum analysis
Ultraviolet spectroscopy
Zinc compounds
Quantum theory
Is there a bridging ligand in metal-substituted zinc β-lactamases? A spectroscopic and theoretical answer
topic_facet Co(II)
Electronic spectra
Metallo-β-lactamase
NMR
Theoretical calculation
Bridging ligands
Band structure
Charge transfer
Electronic structure
Enzymes
Nuclear magnetic resonance
Positive ions
Spectrum analysis
Ultraviolet spectroscopy
Zinc compounds
Quantum theory
description The spectral features of Co(II)-substituted metallo-β-lactamases were analyzed. Nuclear magnetic resonance (NMR) evidence is provided that shows no magnetic coupling between the two metal ions in Co(II),Co(II)-βLII (β-lactamase II from Bacillus cereus), suggesting that no bridging ligand connects them. Ultraviolet-visible (UV-vis) data are rationalized on the basis of semiempirical quantum chemical calculations of the intermediate neglect of differential overlap type (ZINDO/S). The binuclear active sites of the enzymes from B. cereus (βLII) and B. fragilis (CcrA) were modeled from the protein data bank (PDB) coordinates, and calculations were performed at the multireference configuration interaction level. The active site geometries of these enzymes were examined using the experimental electronic spectra as a guide. The model which best fits to the spectroscopic data lacks a bridging solvent molecule, in agreement with the NMR data. The model could also reproduce spectral changes seen in the mixed Zn(II),Co(II) adduct. The bands in the visible range are associated with ligand field transitions at the high-affinity site, whereas the UV-calculated features originate in ligand-to-metal charge transfer to the open shell Co(II) in the low-affinity site. These results indirectly support the hypothesis that the Co(II),Co(II) derivative of CcrA is also unbridged, in contrast with the structure of the native zinc enzyme. These results indicate that the existence of a bridging ligand is not necessary for metallo-β-lactamase activity, and that the second zinc ion is not essential for lowering the pK a of the bound water. © 2002 Wiley Periodicals, Inc. Int. J. Quantum Chem.
title Is there a bridging ligand in metal-substituted zinc β-lactamases? A spectroscopic and theoretical answer
title_short Is there a bridging ligand in metal-substituted zinc β-lactamases? A spectroscopic and theoretical answer
title_full Is there a bridging ligand in metal-substituted zinc β-lactamases? A spectroscopic and theoretical answer
title_fullStr Is there a bridging ligand in metal-substituted zinc β-lactamases? A spectroscopic and theoretical answer
title_full_unstemmed Is there a bridging ligand in metal-substituted zinc β-lactamases? A spectroscopic and theoretical answer
title_sort is there a bridging ligand in metal-substituted zinc β-lactamases? a spectroscopic and theoretical answer
publishDate 2002
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00207608_v88_n1_p118_Estiu
http://hdl.handle.net/20.500.12110/paper_00207608_v88_n1_p118_Estiu
_version_ 1768545538834169856

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