Plant‐type ferredoxin‐NADP ⁺ reductases: a basal structural framework and a multiplicity of functions

Abstract

Ferredoxin-NADP+ (oxido)reductase (EC 1.18.1.2, FNR) is an FAD-containing enzyme that catalyzes the reversible electron transfer between NADP(H) and electron carrier proteins such as ferredoxin and flavodoxin. Isoforms of this flavoprotein are present in chloroplasts, mitochondria, and bacteria in which they participate in a wide variety of redox metabolic pathways. Although ferredoxin-NADP+ reductases have been thoroughly investigated and their properties reviewed on several occasions, considerable advances in the understanding of these flavoenzymes have occurred in the last few years, including the characterization of cDNA and genomic clones encoding FNR proteins from plants, algae, vertebrates, and bacteria, determination of the atomic structure of a plant FNR at high resolution, and the expression of functional reductases in microorganisms like Escherichia coli and Saccharomyces cerevisiae. The aim of this article is to summarize information gained through these recent developments, including the phylogenetic relationships among ferredoxin reductases and the key structural features of the plant FNR family. Other aspects such as the catalytic mechanism of FNR and the molecular events underlying biogenesis, intracellular sorting, folding, and holoenzyme assembly of this important flavoenzyme are also discussed in some detail. Ferredoxin-NADP+ reductases display several outstanding properties that make them excellent model proteins to address broad biological questions.

Purification and characterization of ferredoxin-NADP+ reductase encoded by Bacillus subtilis yumC

“…The first includes the plant-type FNRs that are monomeric enzymes also found in eukaryotic algae as well as in cyanobacteria, and have been intensively reviewed (Arakaki et al 1997). The second group is sometimes called the bacteria type and is composed of monomeric FNRs from some bacteria such as Escherichia coli (Bianchi et al 1993) and Azotobacter vinelandii (Isas et al 1995).…”

“…The second group is sometimes called the bacteria type and is composed of monomeric FNRs from some bacteria such as Escherichia coli (Bianchi et al 1993) and Azotobacter vinelandii (Isas et al 1995). There are significant similarities between these two groups of FNRs in 3-D structure (Prasad et al 1998) as well as in amino acid sequence (Arakaki et al 1997, Ceccarelli et al 2004). These two FNR groups can be united to a plant type in a broader sense.…”

Cores and pH-dependent Dynamics of Ferredoxin-NADP+ Reductase Revealed by Hydrogen/Deuterium Exchange

“…It catalyzes the transfer of electrons during photosynthesis: FNR receives two electrons from ferredoxin, a one-electron carrier protein, and transfers them to NADP ϩ to produce NADPH (14). The activity and affinities for substrates of FNR decreased in response to a pH change from about 8 to 6 in chloroplasts (15).…”

Crystal Structure of Paprika Ferredoxin-NADP+Reductase

“…This flavoprotein is the last enzyme in the electron transport chain of linear photosynthesis, where electrons are transferred through a series of electron carriers and finally produce NADPH. FNRs have also been identified in various tissues and organisms not capable of photosynthesis, where FNR is involved in nitrogen fixation and steroid hydroxylation (2). In photosynthesis, FNR catalyzes the reduction of NADP ϩ to NADPH according to the reaction, 2 Fd red ϩ NADP ϩ ϩ H ϩ ¡ 2 Fd ox ϩ NADPH REACTION 1 which can be divided into two half-reactions.…”

“…FNRs have also been identified in various tissues and organisms not capable of photosynthesis, where FNR is involved in nitrogen fixation and steroid hydroxylation (2). In photosynthesis, FNR catalyzes the reduction of NADP ϩ to NADPH according to the reaction, 2 Fd red ϩ NADP ϩ ϩ H ϩ ¡ 2 Fd ox ϩ NADPH REACTION 1 which can be divided into two half-reactions. For catalyzing this reaction, FNR utilizes the noncovalently but strongly bound prosthetic group FAD as the only redox center.…”