Nitrogenase beyond the Resting State: A Structural Perspective.

Area of Science:

• Biochemistry
• Enzymology
• Structural Biology

Background:

• Nitrogenases catalyze the vital reduction of dinitrogen to ammonia.
• Understanding the nitrogenase mechanism involves studying substrate binding and cofactor roles.

Purpose of the Study:

• To review recent experimental characterizations of nitrogenase under turnover conditions.
• To compare active enzyme forms with resting states and related iron-sulfur clusters.

Main Methods:

• Cryo-electron microscopy (cryo-EM) for structural determination.
• Analysis of enzyme dynamics and cofactor interactions.

Main Results:

• Nitrogenase exhibits obligatory coupling of protein and electron transfers, unlike simpler iron-sulfur clusters.
• Enzyme and cofactor dynamics are crucial, with homocitrate mediating these changes.
• Cryo-EM reveals structural asymmetries during turnover, suggesting potential half-of-sites reactivity.

Conclusions:

• The unique cofactor structure and dynamics are key to nitrogenase function.
• Coupled electron and proton transfers in nitrogenase are facilitated by specific cofactor features.
• Further research is needed to establish the mechanistic significance of observed structural asymmetries.