Playing marble run to make methane

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Science  18 Aug 2017:
Vol. 357, Issue 6352, pp. 642-643
DOI: 10.1126/science.aao2439

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Several archaea make a living by converting carbon dioxide and dihydrogen to methane, a process called methanogenesis that has a direct impact on the global methane cycle (1, 2). However, the electrons obtained from H2 oxidation are not energetic enough to reduce CO2 in the first step of methanogenesis. Some methanogenic archaea solve this problem by using a metalloenzyme complex, which energizes one half of the H2-derived electrons at the expense of the other half. On page 699 of this issue, Wagner et al. (3) show how the electrons receive the necessary energy push. They report that in the crystal structure of the metalloenzyme complex, a T-shaped electron transfer chain splits the electron flow from a single donor toward two acceptors. One acceptor has to bind to a pair of novel iron-sulfur clusters to be reduced.