FeMoco

[2] Crystallographic analysis of the MoFe protein initially revealed the geometry and chemical composition of FeMoco,[3][4][5] later confirmed by extended X-ray absorption fine-structure (EXAFS) studies.

FeMoco assembly is proposed to be initiated by NifS and NifU which mobilize Fe and sulfide into small Fe-S fragments.

These biosynthetic factors have been elucidated and characterized with the exact functions and sequence confirmed by biochemical, spectroscopic, and structural analyses.

[5][9] The approach for the identification relied on a combination of 13C/15N-labeling and pulsed EPR spectroscopy as well as X-ray crystallographic studies at full atomic resolution.

[9] The use of X-ray crystallography showed that while the FeMo cofactor is not in its catalytic form, the carbon keeps the structure rigid which helps describe the reactivity of nitrogenase.

Understanding the process in which an electron is transferred in the protein adduct shows a more precise kinetic model of the FeMo cofactor.

It is believed that the Fe atoms closest to the interstitial carbon participate in substrate activation, but the terminal molybdenum is also a candidate for nitrogen fixation.

[14] Additional studies showed simultaneous binding of two CO-molecules to FeMoco, providing a structural basis for biological Fischer-Tropsch-type chemistry.

[15][16] Se-incorporation studies in combination with time-resolved X-ray crystallography evidenced major structural rearrangements in the FeMoco-structure upon substrate binding events.