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A hydrogen bond network in the active site of Anabaena ferredoxin-NADP + reductase modulates its catalytic efficiency

AuthorsSánchez-Azqueta, Ana; Herguedas, Beatriz ; Hurtado-Guerrero, R.; Hervás, Manuel ; Navarro, José A. ; Martínez-Júlvez, Marta; Medina, Milagros
KeywordsKinetic isotope effect 27
Site-directed mutagenesis
Charge-transfer complex
Catalytically competent interaction
Hydride transfer
Isoalloxazine:nicotinamide interaction
Ferredoxin-NADP+ reductase
Issue Date2014
CitationBiochimica et Biophysica Acta - Bioenergetics 1837: 251- 263 (2014)
AbstractFerredoxin-nicotinamide-adenine dinucleotide phosphate (NADP+) reductase (FNR) catalyses the production of reduced nicotinamide-adenine dinucleotide phosphate (NADPH) in photosynthetic organisms, where its flavin adenine dinucleotide (FAD) cofactor takes two electrons from two reduced ferredoxin (Fd) molecules in two sequential steps, and transfers them to NADP+ in a single hydride transfer (HT) step. Despite the good knowledge of this catalytic machinery, additional roles can still be envisaged for already reported key residues, and new features are added to residues not previously identified as having a particular role in the mechanism. Here, we analyse for the first time the role of Ser59 in Anabaena FNR, a residue suggested by recent theoretical simulations as putatively involved in competent binding of the coenzyme in the active site by cooperating with Ser80. We show that Ser59 indirectly modulates the geometry of the active site, the interaction with substrates and the electronic properties of the isoalloxazine ring, and in consequence the electron transfer (ET) and HT processes. Additionally, we revise the role of Tyr79 and Ser80, previously investigated in homologous enzymes from plants. Our results probe that the active site of FNR is tuned by a H-bond network that involves the side-chains of these residues and that results to critical optimal substrate binding, exchange of electrons and, particularly, competent disposition of the C4n (hydride acceptor/donor) of the nicotinamide moiety of the coenzyme during the reversible HT event. © 2013 Elsevier B.V.
Identifiersdoi: 10.1016/j.bbabio.2013.10.010
issn: 0005-2728
Appears in Collections:(IBVF) Artículos
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