Details

Autor(en) / Beteiligte

• Werth, Mark T.
• Cecchini, Gary
• Manodori, Anamaria
• Brian A. C. Ackrell
• Schroder, Imke
• Gunsalus, Robert P.
• Johnson, Michael K.

Titel

Site-Directed Mutagenesis of Conserved Cysteine Residues in Escherichia coli Fumarate Reductase: Modification of the Spectroscopic and Electrochemical Properties of the [2Fe-2S] Cluster

Ist Teil von

• Proceedings of the National Academy of Sciences - PNAS, 1990-11, Vol.87 (22), p.8965-8969

Ort / Verlag

Washington, DC: National Academy of Sciences of the United States of America

Erscheinungsjahr

1990

Quelle

MEDLINE

Beschreibungen/Notizen

• Site-directed mutants of Escherichia coli fumarate reductase in which each of the four N-terminal cysteine residues in the FrdB subunit, residues 57, 62, 65, and 77, was mutated individually to serine have been constructed, overexpressed, and investigated in terms of enzymatic activity as well as the EPR and redox properties of the iron-sulfur centers. In each case, the mutant contains a functional fumarate reductase in which all three of the constituent iron-sulfur clusters (i.e., center 1, [2Fe-2S]; center 2, [4Fe-4S]; center 3, [3Fe-4S]) have been assembled. The mutations affect the properties of center 1 only and demonstrate that the anomalously high redox potential of this [2Fe-2S] center is essential for optimal enzymematic activity. The results are consistent with cysteines 57, 62, 65, and 77 providing the ligands to center 1 but leave open the possibility of noncysteinyl coordination for the localized valence Fe(III) site of the reduced cluster. The implications of the results for the role of center 1 in the electron-transfer pathway and the valence localization of reduced center 1 are discussed.