A productive NADP+ binding mode of ferredoxin-NADP + reductase revealed by protein engineering and crystallographic studies

DENG, Z; ALIVERTI, ALESSANDRO; ZANETTI, GIULIANA; ARAKAKI, A; JORGELINA OTTADO; ORELLANO, E; CALCATERRA, NORA B; CECCARELLI, EDUARDO; CARRILLO, NÉSTOR; KARPLUS, P

Nature Structural Biology

Año: 1999 vol. 6 p. 847 - 853

The flavoenzyme ferredoxin–NADP+ reductase (FNR) catalyzes the production of NADPH during photosynthesis. Whereas the structures of FNRs from spinach leaf and a cyanobacterium as well as many of their homologs have been solved, none of these studies has yielded a productive geometry of the flavin–nicotinamide interaction. Here, we show that this failure occurs because nicotinamide binding to wild type FNR involves the energetically unfavorable displacement of the C-terminal Tyr side chain. We used mutants of this residue (Tyr 308) of pea FNR to obtain the structures of productive NADP+ and NADPH complexes. These structures reveal a unique NADP+ binding mode in which the nicotinamide ring is not parallel to the flavin isoalloxazine ring, but lies against it at an angle of ~30°, with the C4 atom 3 Å from the flavin N5 atom.