Probing the coordination and function of Fe 4 S 4 modules in nitrogenase assembly protein NifB

The site nitrogen fixation in nitrogenase is an unusual [Fe7S9CMo] cofactor that contains carbide at its center. The formation of a [Fe8S9C] core on the radical SAM enzyme NifB has been investigated in a recent publication in Nature Communications by the Dave Britt group in collaboration with the Yilin Hu group at UCI. Using pulse EPR, Jarett Wilcoxen was able to identify a rare histidine coordination to one of the substrate [Fe4S4] clusters that go on to become part of the [Fe8S9C] core. These exciting results set the stage for mechanistic studies on the formation of this important cofactor.