Abstract
The Na(+)-translocating NADH:quinone oxidoreductase from Vibrio cholerae contains a single Fe-S cluster localized in subunit NqrF. Here we study the electronic properties of the Fe-S center in a truncated version of the NqrF subunit comprising only its ferredoxin-like Fe-S domain. Mössbauer spectroscopy of the Fe-S domain in the oxidized state is consistent with a binuclear Fe-S cluster with tetrahedral sulfur coordination by the cysteine residues Cys(70), Cys(76), Cys(79), and Cys(111). Important sequence motifs surrounding these cysteines are conserved in the Fe-S domain and in vertebrate-type ferredoxins. The magnetic circular dichroism spectra of the photochemically reduced Fe-S domain exhibit a striking similarity to the magnetic circular dichroism spectra of vertebrate-type ferredoxins required for the in vivo assembly of iron-sulfur clusters. This study reveals a novel function for vertebrate-type [2Fe-2S] clusters as redox cofactors in respiratory dehydrogenases.
Highlights
From the ‡Mikrobiologisches Institut der Eidgenossischen Technischen Hochschule, ETHHonggerberg, CH-8093 Zurich, Switzerland and the ʈMax-Planck-Institut fur Bioanorganische Chemie, D-45470 Mulheim an der Ruhr, Germany
The initial oxidation of NADH by the NqrF subunit results in the two-electron reduction of the FAD followed by one-electron transfer steps to the [2Fe-2S] cluster in the Fe-S domain [7]
This is further supported by Mossbauer and magnetic circular dichroism (MCD) spectra of the Fe-S domain, which are reminiscent to ISC-type ferredoxins
Summary
From the ‡Mikrobiologisches Institut der Eidgenossischen Technischen Hochschule, ETHHonggerberg, CH-8093 Zurich, Switzerland and the ʈMax-Planck-Institut fur Bioanorganische Chemie, D-45470 Mulheim an der Ruhr, Germany. Mossbauer spectroscopy of the Fe-S domain in the oxidized state is consistent with a binuclear Fe-S cluster with tetrahedral sulfur coordination by the cysteine residues Cys70, Cys76, Cys79, and Cys111. The magnetic circular dichroism spectra of the photochemically reduced Fe-S domain exhibit a striking similarity to the magnetic circular dichroism spectra of vertebrate-type ferredoxins required for the in vivo assembly of iron-sulfur clusters.
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