With regards to the active sites present in nitrogenase:
1
The M-cluster, which is responsible for the reduction of N2, contains a Fe4S4 core.
2
The P-cluster in the CoFe protein is a Fe8S7 cluster.
3
The enzyme nitrogenase requires ATP to reduce molecular nitrogen.
4
All electrons in the conversion of N2 to NH3 are directly transferred from the Fe protein to the MoFe cluster.