Dynamics driving the precursor in NifEN scaffold during nitrogenase FeMo-cofactor assembly

Area of Science:

• Biochemistry
• Structural Biology
• Nitrogen Fixation

Background:

• Nitrogenase is crucial for atmospheric nitrogen fixation.
• Its organometallic cofactor requires a complex assembly system.
• NifEN is a scaffold protein involved in the final stages of cofactor biosynthesis.

Purpose of the Study:

• To elucidate the structural basis for NifEN function in cofactor assembly.
• To understand the dynamic mechanisms of precursor maturation.
• To explore the role of NifEN in facilitating cofactor incorporation into nitrogenase.

Main Methods:

• High-resolution structural analyses (e.g., X-ray crystallography, cryo-EM).
• Biophysical techniques to study protein dynamics.
• Biochemical assays to assess cofactor precursor binding and transfer.

Main Results:

• NifEN binds the cofactor precursor at a surface site, then transfers it to an internal cavity for maturation.
• Dynamic structural rearrangements, including domain motions and partial unfolding, allow NifEN to switch between open and closed states.
• A rear channel likely facilitates the entry of molybdenum and homocitrate into the precursor-binding cavity.

Conclusions:

• NifEN employs dynamic structural mechanisms to guide FeMo-cofactor assembly.
• The findings reveal functional divergence between the scaffold NifEN and the catalytic nitrogenase component NifDK.
• This study provides critical insights into the intricate process of biological nitrogen fixation.