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Gas channel rerouting in a primordial enzyme: Structural insights of the carbon-monoxide dehydrogenase/acetyl-CoA synthase complex from the acetogen Clostridium autoethanogenum

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Lemaire,  Olivier N.
Research Group Microbial Metabolism, Max Planck Institute for Marine Microbiology, Max Planck Society;

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Wagner,  Tristan
Research Group Microbial Metabolism, Max Planck Institute for Marine Microbiology, Max Planck Society;

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Citation

Lemaire, O. N., & Wagner, T. (2021). Gas channel rerouting in a primordial enzyme: Structural insights of the carbon-monoxide dehydrogenase/acetyl-CoA synthase complex from the acetogen Clostridium autoethanogenum. Biochimica et Biophysica Acta, Bioenergetics, 1862(1): 148330. doi:10.1016/j.bbabio.2020.148330.


Cite as: http://hdl.handle.net/21.11116/0000-0007-F1AD-6
Abstract
Clostridium autoethanogenum, the bacterial model for biological conversion of waste gases into biofuels, grows under extreme carbon-monoxide (CO) concentrations. The strictly anaerobic bacterium derives its entire cellular energy and carbon from this poisonous gas, therefore requiring efficient molecular machineries for CO-conversion. Here, we structurally and biochemically characterized the key enzyme of the CO-converting metabolism: the CO-dehydrogenase/Acetyl-CoA synthase (CODH/ACS). We obtained crystal structures of natively isolated complexes from fructose-grown and CO-grown C. autoethanogenum cultures. Both contain the same isoforms and if the overall structure adopts the classic alpha(2)beta(2) architecture, comparable to the model enzyme from Moorella thermoacetica, the ACS binds a different position on the CODH core. The structural characterization of a proteolyzed complex and the conservation of the binding interface in close homologs rejected the possibility of a crystallization artefact. Therefore, the internal CO-channeling system, critical to transfer CO generated at the C-cluster to the ACS active site, drastically differs in the complex from C. autoethanogenum. The 1.9-angstrom structure of the CODH alone provides an accurate picture of the new CO-routes, leading to the ACS core and reaching the surface. Increased gas accessibility would allow the simultaneous CO-oxidation and acetyl-CoA production. Biochemical experiments showed higher flexibility of the ACS subunit from C. autoethanogenum compared to M. thermoacetica, albeit monitoring similar CO-oxidation and formation rates. These results show a reshuffling of internal CO-tunnels during evolution of these Firmicutes, putatively leading to a bidirectional complex that ensure a high flux of CO-conversion toward energy conservation, acting as the main cellular powerplant.