EXAFS and NRVS Reveal a Conformational Distortion of the FeMo-cofactor in the MoFe Nitrogenase Propargyl Alcohol Complex

► First experimental details of conformational changes of FeMo-cofactor on binding substrate. ► EXAFS and NRVS study of propargyl alcohol (PA) binding to MoFe nitrogenase. ► EXAFS shows changes in the 3.7 Å Fe-Fe distance on binding PA but no change in 5.1 Å Mo-Fe interaction. ► NRVS shows only minor changes, indicating the Fe6S9X core remains essentially intact. ► Bound form of PA is coordinated to Fe6 or Fe7, with concomitant movement of the Fe atom.