Kern, Melanie ; Klotz, Martin G. ; Simon, Jörg (2011)
The Wolinella succinogenes mcc gene cluster encodes an unconventional respiratory sulfite reduction system.
In: Molecular microbiology, 82 (6)
Artikel, Bibliographie

Kurzbeschreibung (Abstract)

Assimilatory and dissimilatory sulfite reduction are key reactions in the biogeochemical sulfur cycle and several distinct sirohaem-containing sulfite reductases have been characterized. Here, we describe that the Epsilonproteobacterium Wolinella succinogenes is able to grow by sulfite respiration (yielding sulfide) with formate as electron donor. Sulfite is reduced by MccA, a prototypical member of an emerging new class of periplasmic cytochrome c sulfite reductases that, phylogenetically, belongs to a multihaem cytochrome c superfamily whose members play crucial roles in the global sulfur and nitrogen cycles. Within this family, MccA represents an unconventional octahaem cytochrome c containing a special haem c group that is bound via two cysteine residues arranged in a unique CX(15) CH haem c binding motif. The phenotypes of numerous W. succinogenes mutants producing MccA variants underlined the structural importance of this motif. Several open reading frames of the mcc gene cluster were individually inactivated and characterization of the corresponding mutants indicated that the predicted iron-sulfur protein MccC, the putative quinol dehydrogenase MccD (a member of the NrfD/PsrC family) as well as a peptidyl-prolyl cis-trans isomerase, MccB, are essential for sulfite respiration. MccA synthesis in W. succinogenes was found to be induced by sulfite (but not by thiosulfate or sulfide) and repressed in the presence of fumarate or nitrate. Based on the results, a sophisticated model of respiratory sulfite reduction by the Mcc system is presented.

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