The Ferredoxin NADP+ Reductase from Escherichia coli contains NADP+ tightly bound.

CECCARELLI, EDUARDO A.; MUSUMECI, MATÍAS A; CATALANO DUPUY, DANIELA L.

Flavins and Flavoproteins 2011

University of California, Berkeley

Lugar: Berkeley; Año: 2011;

Ferredoxin-NADP+ reductases (FNRs, EC 1.18.1.2) are flavoenzymes that contain non-covalently bound FAD as prosthetic group. Their function is to catalyze the reversible electron transfer between NADPH (a two-electron carrier) and ferredoxin or flavodoxin (one-electron carriers). In photosynthetic organisms FNRs have evolved to produce NADPH from reduced ferredoxin during the photosynthesis to provide NADPH to different biosynthetic pathways as the Calvin cycle. However, in bacteria and non-photosynthetic tissues the inverse reaction is favoured, namely the reduction of ferredoxin or flavodoxin from NADPH in order to supply low potential electron donors to different metabolisms. The plastidic FNRs are more efficient enzymes than the bacterial ones. The conformation of the FAD, the mobility and the structure of the C-terminal region, among other features, are proposed to be responsible for the different catalytic behaviours of these enzymes. The NADP+ binding mode to the enzyme may contribute to the different catalytic efficiencies displayed by the plastidic and the bacterial enzymes. We detected that about 20% of the purified E. coli FNR from this bacteria contains tightly bound NADP+. The nucleotide remained bound to the enzyme after several purification steps. Considering that NADP+ was not added during the purification procedure, it can be concluded that the FNR bound the nucleotide during its expression in E. coli cells. In this work we analyzed the influence of the NADP+ binding mode in the catalytic behaviour of E. coli FNR.