Catching carbon fixation without fixing

Biological carbon fixation is a process in which living organisms convert atmospheric carbon dioxide (CO₂) into metabolically usable organic compounds, such as sugars or acetate. This not only forms the foundation of the food chain but is also vital for regulating the global carbon cycle. The fixation of CO₂ involves many enzymes and cofactors. Although important features of the six known biological carbon fixation pathways have been established (1, 2), the sizes and transient natures of protein complexes have complicated the capture of intermediate states using structural methods such as x-ray crystallography and nuclear magnetic resonance spectroscopy. On page 498 of this issue, Yin et al. (3) report high-resolution snapshots of the Wood-Ljungdahl pathway (WLP), which is one of the most efficient carbon fixation mechanisms, using cryo–electron microscopy (cryo-EM). The results reveal the dynamics of key enzymes and could contribute to designing such pathways for carbon capture and biofuel production (4).