Fig. 1: Nitrogenase and NFL systems.

a,b, Subunit composition (a) and metallocofactor composition (b) of the three isoforms of N2ase and the NFL systems, which are MAR for reductive C–S bond cleavage of VOSCs5, DPOR and COR for bacteriochlorophyll synthesis9,10 and CfbCD for methanogenesis F430 cofactor synthesis11. For V and Fe N2ase, an additional G-subunit (δ) is involved in M-cluster association and interactions between components26,48,70. The mar1 and mar2 clusters are P-like and FeFe-co-like metallocofactors whose precise identity is not fully resolved. c, Reactions catalysed by N2ase. d, Reactions catalysed by MAR.