Methanogenic heterodisulfide reductase (HdrABC-MvhAGD) uses two noncubane [4Fe-4S] clusters for reduction

Abstract

Methanogenic archaea metabolism Most of the methane on Earth is produced by the metabolism of methanogenic archaea. The final step involves a reaction between methyl-coenzyme M and coenzyme B to give CoM-S-S-CoB and methane. Wagner et al. report a high-resolution structure of the methanogenic heterodisulfide reductase (HdtABC)-[NiFe]-hydrogenase, the enzyme that reduces the disulfide and couples this to the reduction of ferredoxin in an energy-conserving process known as flavin-based electron bifurcation (FBEB) (see the Perspective by Dobbek). The reduced ferredoxin, in turn, drives the first step of methanogenesis. The structure shows how two noncubane [4Fe-4S] clusters perform disulfide cleavage and gives insight into the mechanism of FBEB. Science , this issue p. 699 ; see also p. 642