Trafficking of a nitrogenase FeMo-cofactor assembly intermediate.

Area of Science:

• Biochemistry
• Structural Biology
• Nitrogen Fixation

Background:

• Molybdenum nitrogenase FeMo-cofactor maturation is essential for nitrogen fixation.
• This process involves sequential action of maturase complexes, including NifEN, NifB, and NifX.
• NifB-cofactor (L-cluster) is a precursor to the FeMo-cofactor.

Purpose of the Study:

• To elucidate the structural mechanism of L-cluster transfer from NifX to NifEN.
• To visualize the dynamic complex involved in FeMo-cofactor precursor maturation.
• To understand the role of NifX in delivering the L-cluster to the NifEN maturase.

Main Methods:

• High-resolution cryo-electron microscopy (cryo-EM) of NifEN-NifX complexes.
• In silico modeling and computational studies.

Main Results:

• Detailed cryo-EM structures of NifEN in complex with NifX, capturing L-cluster transfer.
• Identification of a dynamic transfer complex where the L-cluster is coordinated by residues from both NifEN and NifX.
• In silico studies support the structural findings and suggest an internal conversion site for cluster maturation.

Conclusions:

• The NifEN and NifX proteins form a dynamic complex to facilitate L-cluster transfer.
• This structural insight provides a detailed view of a critical step in molybdenum nitrogenase biosynthesis.
• Further studies may focus on the internal conversion site for complete understanding of FeMo-cofactor maturation.