title: Enhancement of photophysical and photosensitizing properties of flavin adenine dinucleotide by mutagenesis of the C-terminal extension of a bacterial flavodoxin reductase.
abstract: 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 (1) FAD* 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.
authors: Centro de Investigaciones y Transferencia de Santiago del Estero (CITSE-CONICET), Universidad Nacional de Santiago del Estero, RN9 Km 1125. 4206, Santiago del Estero (Argentina).
authors: Lorena
authors: L
authors: Valle
authors: Inés
authors: I
authors: Abatedaga
authors: Faustino E Morán
authors: FE
authors: Vieyra
authors: Ana
authors: A
authors: Bortolotti
authors: Néstor
authors: N
authors: Cortez
authors: Claudio D
authors: CD
authors: Borsarelli
mesh_terms: D005287:Ferredoxin-NADP Reductase / Q000235:genetics* / Q000378:metabolism; D005182:Flavin-Adenine Dinucleotide / Q000737:chemistry* / Q000378:metabolism; D055668:Photochemical Processes; D017319:Photosensitizing Agents / Q000737:chemistry* / Q000378:metabolism; D016354:Rhodobacter capsulatus / Q000201:enzymology*
chemical_list: D017319:Photosensitizing Agents; D005182:Flavin-Adenine Dinucleotide; D005287:Ferredoxin-NADP Reductase
keywords: flavin triplet state; flavoproteins; fluorescence; oxidoreductases; singlet oxygen