Enhancement of Photophysical and Photosensitizing Properties of Flavin Adenine Dinucleotide by Mutagenesis of the C-Terminal Extension of a Bacterial Flavodoxin Reductase

VALLE, LORENA; ABATEDAGA, INÉS; MORÁN-VIEYRA, FAUSTINO E.; BORTOLOTTI, ANA; CORTEZ, NÉSTOR; BORSARELLI, CLAUDIO

Chemphyschem

Wiley Online Library

Lugar: Weinheim; Año: 2015 vol. 16 p. 872 - 883

1439-4235

The role of the mobile C-terminal extension present in Rhodobacter capsulatus ferredoxin?NADP(H) reductase (RcFPR) was evaluated using steady-state and dynamic spectroscopies for both intrinsic Trp and FAD in a series of mutants in the absence of NADP(H). Deletion of the six C-terminal amino acids beyond Ala266 was combined with the replacement A266Y to emulate the structure of plastidic reductases. Our results show that these modifications of the wild-type RcFPR produce subtle global conformational changes, but strongly reduce the local rigidity of the FAD-binding pocket, exposing the isoalloxazine ring to the solvent. Thus, the ultrafast charge-transfer quenching of 1FAD* by the conserved Tyr66 residue was absent in the mutant series, producing enhancement of the excited singlet- and triplet-state properties of FAD. This work highlights the delicate balance of the specific interactions between FAD and the surrounding amino acids, and how the functionality and/or photostability of redox flavoproteins can be modified.