The methanogenic CO2 reducing-and-fixing enzyme is bifunctional and contains 46 [4Fe-4S] clusters

• Autores: Tristan Wagner, Ulrich Ermler, Seigo Shima
• Localización: Science, ISSN 0036-8075, Vol. 354, Nº 6308, 2016, págs. 115-117
• Idioma: inglés
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• Resumen

  • Biological methane formation starts with a challenging adenosine triphosphate (ATP)–independent carbon dioxide (CO2) fixation process. We explored this enzymatic process by solving the x-ray crystal structure of formyl-methanofuran dehydrogenase, determined here as Fwd(ABCDFG)2 and Fwd(ABCDFG)4 complexes, from Methanothermobacter wolfeii. The latter 800-kilodalton apparatus consists of four peripheral catalytic sections and an electron-supplying core with 46 electronically coupled [4Fe-4S] clusters. Catalysis is separately performed by subunits FwdBD (FwdB and FwdD), which are related to tungsten-containing formate dehydrogenase, and subunit FwdA, a binuclear metal center carrying amidohydrolase. CO2 is first reduced to formate in FwdBD, which then diffuses through a 43-angstrom-long tunnel to FwdA, where it condenses with methanofuran to formyl-methanofuran. The arrangement of [4Fe-4S] clusters functions as an electron relay but potentially also couples the four tungstopterin active sites over 206 angstroms.