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Título:
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The Activating Component of the Anaerobic Ribonucleotide Reductase from Escherichia coli
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Autor/a:
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Tamarit Sumalla, Jordi; Gerez, Catherine; Meier, Christian; Mulliez, Etienne; Trautwein, Alfred; Fontecave, Marc
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Notas:
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Class III anaerobic ribonucleotide reductase small
component, named protein b, contains a (4Fe-4S) center.
Its function is to mediate electron transfer from reduced
flavodoxin to S-adenosylmethionine, required for the
introduction of a glycyl radical in the large component,
named protein a, which then becomes active for the
reduction of ribonucleotides. By site-directed mutagenesis
we demonstrate that the three cysteines of the conserved
CXXXCXXC sequence are involved in iron chelation.
Such a sequence is also present in the activase of
the pyruvate formate-lyase and in the biotin synthase,
both carrying an iron-sulfur center involved in reductive
activation of S-adenosylmethionine. Even though
they are able to bind iron in the (4Fe-4S) form, as shown
by Mo¨ssbauer spectroscopy, the corresponding Cys to
Ala mutants are catalytically inactive. Mutation of the
two other cysteines of the protein did not result in inactivation.
We thus conclude that the (4Fe-4S) cluster has,
in the wild type protein, only three cysteine ligands and
a fourth still unidentified ligand. |
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Derechos:
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(c) The American Society for Biochemistry and Molecular Biology, 2000
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Tipo de documento:
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article
publishedVersion |
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Editor:
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American Society for Biochemistry and Molecular Biology
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