Negative-Stain Electron Microscopy Reveals Dramatic Structural Rearrangements in Ni-Fe-S-Dependent Carbon Monoxide Dehydrogenase/Acetyl-CoA Synthase

• Published in: Structure (London) 2021-01, Vol.29 (1), p.43-49.e3
• Main Authors: Cohen, Steven E., Brignole, Edward J., Wittenborn, Elizabeth C., Can, Mehmet, Thompson, Samuel, Ragsdale, Stephen W., Drennan, Catherine L.
• Format: Article
• Language: English
• Subjects: acetogenesis; acetyl-CoA synthase; Aldehyde Oxidoreductases - chemistry; Aldehyde Oxidoreductases - metabolism; Bacterial Proteins - chemistry; Bacterial Proteins - metabolism; carbon dioxide sequestration; carbon fixation; CO dehydrogenase; electron microscopy; Iron - chemistry; Iron - metabolism; metalloenzyme; methyl transfer; Molecular Dynamics Simulation; Moorella - enzymology; Multienzyme Complexes - chemistry; Multienzyme Complexes - metabolism; Nickel - chemistry; Nickel - metabolism; Protein Domains; protein dynamics; Sulfur - chemistry; Sulfur - metabolism; Wood-Ljungdahl
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2020.08.011

The Ni-Fe-S-containing A-cluster of acetyl-coenzyme A (CoA) synthase (ACS) assembles acetyl-CoA from carbon monoxide (CO), a methyl group (CH3+), and CoA. To accomplish this feat, ACS must bind CoA and interact with two other proteins that contribute the CO and CH3+, respectively: CO dehydrogenase (CODH) and corrinoid Fe-S protein (CFeSP). Previous structural data show that, in the model acetogen Moorella thermoacetica, domain 1 of ACS binds to CODH such that a 70-Å-long internal channel is created that allows CO to travel from CODH to the A-cluster. The A-cluster is largely buried and is inaccessible to CFeSP for methylation. Here we use electron microscopy to capture multiple snapshots of ACS that reveal previously uncharacterized domain motion, forming extended and hyperextended structural states. In these structural states, the A-cluster is accessible for methylation by CFeSP. [Display omitted] •Negative-stain EM of CODH/ACS is described•The ACS subunit demonstrates greater mobility than observed crystallographically•Extended ACS conformations enable CFeSP interactions Cohen et al. demonstrate that carbon monoxide dehydrogenase/acetyl-CoA synthase (CODH/ACS) undergoes wider conformational changes than previously reported. Furthermore, these new conformations explain how the ACS subunit can interact with corrinoid Fe-S protein (CFeSP) in order to mediate a methyl transfer reaction instrumental for anaerobic carbon fixation.