Characterization of the metal clusters in the nitrogenase molybdenum-iron and vanadium-iron proteins of Azotobacter vinelandii using magnetic circular dichroism spectroscopy.
Biochemistry
; 26(7): 1795-800, 1987 Apr 07.
Article
em En
| MEDLINE
| ID: mdl-3474027
ABSTRACT
Low-temperature magnetic circular dichroism (MCD) spectroscopy has been used to investigate the metal clusters in the conventional nitrogenase MoFe protein and alternative VFe protein from Azotobacter vinelandii. In the dithionite-reduced state, the MCD spectrum of the MoFe protein is extremely similar to that previously observed for the S = 3/2 spin state of the M clusters in the MoFe protein of Klebsiella pneumoniae. A paramagnetic cluster with an S = 3/2 ground state is also responsible for the temperature-dependent MCD transitions of dithionite-reduced VFe protein. However, the electronic and magnetic properties of this cluster are quite distinct from those of M centers in conventional nitrogenase. When these proteins are oxidized with thionine, the MoFe protein exhibits MCD spectra and magnetization characteristics identical with those observed for the P clusters in K. pneumoniae, while those of the VFe protein are only similar. However, the paramagnetism in the thionine-oxidized VFe protein, like the conventional enzyme, probably arises from an S = 5/2 spin system with near-axial symmetry and a negative zero-field splitting. Novel clusters with electronic, magnetic, and redox properties similar to those of conventional P clusters are, therefore, present in the VFe protein.
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Base de dados:
MEDLINE
Assunto principal:
Azotobacter
/
Proteínas de Bactérias
/
Ferredoxinas
/
Metaloproteínas
/
Molibdoferredoxina
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Nitrogenase
Idioma:
En
Revista:
Biochemistry
Ano de publicação:
1987
Tipo de documento:
Article