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Updated: Jan 17, 2026
13:02
Production, Crystallization, and Structure Determination of the IKK-binding Domain of NEMO
Published on: December 28, 2019
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Cryo-EM structure of a methanogen nitrogenase-PII protein supercomplex
Rajnandani Kashyap1, Thomas M Deere2, Ahmed Dhamad2
1Department of Biochemistry and Molecular Biology, St. Louis University School of Medicine, St. Louis, MO, USA.
Biorxiv : the Preprint Server for Biology
|September 18, 2025
Summary
Researchers uncovered how archaeal nitrogenases are regulated. PII proteins bind to nitrogenase, forming a supercomplex that inhibits activity, but this inhibition is reversed by cellular signals, revealing new insights into nitrogen fixation.
Area of Science:
- Biochemistry
- Structural Biology
- Microbiology
Background:
- Nitrogenases are crucial metalloenzymes for global nitrogen cycling.
- Bacterial nitrogenase is well-studied, but archaeal nitrogenase regulation remains unclear.
- Methanogens are known to fix nitrogen, but their enzyme structure is unknown.
Purpose of the Study:
- To determine the structure of archaeal nitrogenase.
- To elucidate the regulatory mechanism of nitrogen fixation in methanogens.
Main Methods:
- Cryo-electron microscopy (cryo-EM) was used to determine the structure.
- Biochemical assays were performed to measure enzyme activity.
Main Results:
- A 3.1 Å cryo-EM structure of a nitrogenase-PII supercomplex from *Methanosarcina acetivorans* was obtained.
- The structure revealed three NifDK heterotetramers bridged by six PII complexes, forming an inactive state.
- PII complex binding was modulated by ADP and 2-oxoglutarate, linking inhibition to cellular energy and nitrogen status.
- 2-oxoglutarate and ATP released PII complexes, increasing NifDK activity threefold.
Conclusions:
- A novel regulatory mechanism involving PII-driven nitrogenase oligomerization in methanogens was discovered.
- This higher-order structure controls nitrogenase activity, offering new insights into its evolution and biotechnological potential.
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