Arabidopsis FNRL protein is an NADPH-dependent chloroplast oxidoreductase resembling bacterial ferredoxin-NADP+ reductases

A1 Journal article (refereed)

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Publication Details

List of Authors: Koskela M, Dahlström K, Goñi G, Lehtimäki N, Nurmi M, Velazquez-Campoy A, Hanke G, Bölter B, Salminen T, Medina M, Mulo P
Publisher: Blackwell
Publication year: 2018
Journal: Physiologia Plantarum
Journal acronym: Physiol Plant
Volume number: 162
Issue number: 2
Start page: 177
End page: 190
ISSN: 1399-3054
eISSN: 1399-3054


Plastidic ferredoxin-NADP+ oxidoreductases (FNRs; EC: together with bacterial type FNRs (FPRs) form the plant-type FNR family. Members of this group contain a two-domain scaffold that forms the basis of an extended superfamily of flavin adenine dinucleotide (FAD) dependent oxidoreductases. In this study, we show that the Arabidopsis thaliana At1g15140 [Ferredoxin-NADP+ oxidoreductase-like (FNRL)] is an FAD-containing NADPH dependent oxidoreductase present in the chloroplast stroma. Determination of the kinetic parameters using the DCPIP NADPH-dependent diaphorase assay revealed that the reaction catalysed by a recombinant FNRL protein followed a saturation Michaelis-Menten profile on the NADPH concentration with kcat  = 3.2 ± 0.2 s-1 , KmNADPH  = 1.6 ± 0.3 μM and kcat /KmNADPH  = 2.0 ± 0.4 μM-1  s-1 . Biochemical assays suggested that FNRL is not likely to interact with Arabidopsis ferredoxin 1, which is supported by the sequence analysis implying that the known Fd-binding residues in plastidic FNRs differ from those of FNRL. In addition, based on structural modelling FNRL has an FAD-binding N-terminal domain built from a six-stranded β-sheet and one α-helix, and a C-terminal NADP+ -binding α/β domain with a five-stranded β-sheet with a pair of α-helices on each side. The FAD-binding site is highly hydrophobic and predicted to bind FAD in a bent conformation typically seen in bacterial FPRs.

Last updated on 2020-17-01 at 02:48