STRUCTURE OF ADP-CENTER-DOT-AIF(4)(-)-STABILIZED NITROGENASE COMPLEX AND ITS IMPLICATIONS FOR SIGNAL-TRANSDUCTION

The coupling of ATP hydrolysis to electron transfer by the enzyme nitr ogenase 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-pr otein components of nitrogenase stabilized by ADP AlF4-, previously us ed as a nucleoside triphosphate analogue in nucleotide-switch proteins . The structure reveals that the dimeric re-protein has undergone subs tantial conformational changes. The beta-phosphate and AlF4- groups ar e stabilized through intersubunit contacts that are critical for catal ysis and the redox centre is repositioned to facilitate electron trans fer. Interactions in the nitrogenase complex have broad implications f or signal and energy transduction mechanisms In multiprotein complexes .