A STD-NMR Study of the Interaction of the Anabaena Ferredoxin-NADP(+) Reductase with the Coenzyme

Ferredoxin-NADP(+) reductase (FNR) catalyzes the electron transfer from ferredoxin to NADP(+) via its flavin FAD cofactor. To get further insights in the architecture of the transient complexes produced during the hydride transfer event between the enzyme and the NADP(+) coenzyme we have applied NMR spectroscopy using Saturation Transfer Difference (STD) techniques to analyze the interaction between FNR(ox) and the oxidized state of its NADP(+) coenzyme. We have found that STD NMR, together with the use of selected mutations on FNR and of the non-FNR reacting coenzyme analogue NAD(+), are appropriate tools to provide further information about the the interaction epitope.