The coupling of ATP hydrolysis to electron transfer by the enzyme nitrogenase
during biological nitrogen fixation is an important example of a
nucleotide-dependent transduction mechanism. The crystal structure has been
determined for the complex between the Fe-protein and MoFe-protein components of
nitrogenase stabilized by ADP x AIF4-, previously used as a nucleoside
triphosphate analogue in nucleotide-switch proteins. The structure reveals that
the dimeric Fe-protein has undergone substantial conformational changes. The
beta-phosphate and AIF4- groups are stabilized through intersubunit contacts
that are critical for catalysis and the redox centre is repositioned to
facilitate electron transfer. Interactions in the nitrogenase complex have broad
implications for signal and energy transduction mechanisms in multiprotein
complexes.
