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Published on: February 12, 2019
Capturing a methanogenic carbon monoxide dehydrogenase/acetyl-CoA synthase complex via cryogenic electron microscopy
Alison Biester1, David A Grahame2, Catherine L Drennan1,3,4
1Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139.
Summary
Researchers have determined the structure of methanogenic carbon monoxide dehydrogenase/acetyl-CoA synthase (CODH/ACS). This reveals how methanogens produce methane from acetate, offering insights into greenhouse gas formation.
Area of Science:
- Biochemistry
- Structural Biology
- Microbiology
Background:
- Methanogens produce significant methane from acetate cleavage.
- Acetate breakdown involves acetyl-CoA synthase (ACS) and carbon monoxide dehydrogenase (CODH) enzymes with Ni-Fe-S clusters.
- No prior structure existed for methanogenic CODH/ACS.
Purpose of the Study:
- To determine the structure of methanogenic CODH and CODH/ACS from *Methanosarcina thermophila*.
- To elucidate the molecular mechanisms of acetate metabolism in methanogens.
Main Methods:
- Cryo-electron microscopy (cryo-EM) was used to obtain high-resolution structures.
- Comparative structural analysis of methanogenic CODH/ACS and CODH.
Main Results:
- The methanogenic CODH/ACS structure reveals a unique domain organization compared to acetogens.
- A CODH domain replaces the N-terminal ACS domain, forming a CO channel and binding surface.
- A mechanism for restricting CO gas flow was identified, preventing escape into the cell.
Conclusions:
- The structures provide a molecular basis for understanding methane production in methanogens.
- Despite domain differences, functional similarities exist between methanogenic and acetogenic CODH/ACS.
- These findings advance our knowledge of microbial metabolism and greenhouse gas cycling.
