Mössbauer spectroscopic studies of Escherichia coli sulfite reductase. Evidence for coupling between the siroheme and Fe4S4 cluster prosthetic groups.

Journal Article (Journal Article)

Escherichia coli NADPH-sulfite reductase is a complex hemoflavoprotein with an alpha 8 beta 4 subunit structure. The beta-subunits each contain one siroheme and a tetranuclear iron-sulfur center (Fe4S4). Isolated beta-monomers can catalyze the 6-electron reduction of sulfite to sulfide. We have studied the beta-monomers with Mössbauer and EPR spectroscopy. The data show conclusively that the siroheme and the Fe4S4 cluster are strongly exchange-coupled. This is proven by the observations that (a) the two chromophores share a single electronic spin and (b) the addition of 1 electron to oxidized sulfite reductase changes the environments of 5 iron atoms. Spin-sharing is demonstrated in oxidized and 2-electron-reduced sulfite reductase and strongly implicated in 1-electron-reduced material. Thus, sulfite reductase provides the first example of an active site where a heme and an iron-sulfur cluster are closely linked as a functional unit, probably via a common bridging ligand.

Full Text

Duke Authors

Cited Authors

  • Christner, JA; Münck, E; Janick, PA; Siegel, LM

Published Date

  • March 10, 1981

Published In

Volume / Issue

  • 256 / 5

Start / End Page

  • 2098 - 2101

PubMed ID

  • 6257697

International Standard Serial Number (ISSN)

  • 0021-9258


  • eng

Conference Location

  • United States