Crystal structure of a key enzyme for anaerobic ethane activation.

Cedric J Hahn, Olivier N Lemaire, Jörg Kahnt, Sylvain Engilberge, Gunter Wegener, Tristan Wagner

Science (New York, N.Y.) 2021 Jul 02

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Ethane, the second most abundant hydrocarbon gas in the seafloor, is efficiently oxidized by anaerobic archaea in syntrophy with sulfate-reducing bacteria. Here, we report the 0.99-angstrom-resolution structure of the proposed ethane-activating enzyme and describe the specific traits that distinguish it from methane-generating and -consuming methyl-coenzyme M reductases. The widened catalytic chamber, harboring a dimethylated nickel-containing F430 cofactor, would adapt the chemistry of methyl-coenzyme M reductases for a two-carbon substrate. A sulfur from methionine replaces the oxygen from a canonical glutamine as the nickel lower-axial ligand, a feature conserved in thermophilic ethanotrophs. Specific loop extensions, a four-helix bundle dilatation, and posttranslational methylations result in the formation of a 33-angstrom-long hydrophobic tunnel, which guides the ethane to the buried active site as confirmed with xenon pressurization experiments. Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Citation

Cedric J Hahn, Olivier N Lemaire, Jörg Kahnt, Sylvain Engilberge, Gunter Wegener, Tristan Wagner. Crystal structure of a key enzyme for anaerobic ethane activation. Science (New York, N.Y.). 2021 Jul 02;373(6550):118-121