NADP(H) allosterically regulates the interaction between ferredoxin and ferredoxin‐NADP⁺ reductase

Abstract

Ferredoxin‐NADP+ reductase (FNR) in plants receives electrons from ferredoxin (Fd) at the end of the photosynthetic electron transfer chain and converts NADP+ to NADPH. The interaction between Fd and FNR in plants was previously shown to be attenuated by NADP(H). Here, we investigated the molecular mechanism of this phenomenon using maize FNR and Fd, as the three‐dimensional structure of this complex is available. NADPH, NADP+, and 2′5′‐ADP differentially affected the interaction, as revealed through kinetic and physical binding analyses. Site‐directed mutations of FNR which change the affinity for NADPH altered the affinity for Fd in the opposite direction to that for NADPH. We propose that the binding of NADP(H) causes a conformational change of FNR which is transferred to the Fd‐binding region through different domains of FNR, resulting in allosteric changes in the affinity for Fd.

Quantification of NAD(P)H in cyanobacterial cells by a phenol extraction method

“…Although NADP(H) is located in the cytoplasm, and cyanobacteria lack organelles, some portion of NADP(H) can be kept oxidized even in light conditions in a cyanobacterial cells by an unknown mechanism. For example, it was reported that NADPH allosterically decreases the binding affinity of ferredoxin (Fd) to ferredoxin-NADP + reductase (FNR) (Kimata-Ariga et al 2019 ), which may prevent complete reduction of the NADP + pool. Another possible explanation is that NADP(H) non-specifically binds proteins such as Rubisco (Badger and Lorimer 1981 ; Latouche et al 2000 ), which may represent the bulk of the less active NADP(H) pool.…”

Oxidation of Flavin by Molecular Oxygen: Computational Insights into a Possible Radical Mechanism

“…Another important example of flavoenzymes is monoamine oxidases (MAOs) controlling levels of monoaminergic neurotransmitters in the central nervous system. MAO enzymes use covalently bound FAD prosthetic group facilitating oxidative decomposition of neurotransmitters such as dopamine and serotonin. − Other examples of flavin-dependent enzymes include d -amino acid oxidase regulating the levels of nonacidic amino acids in tissues by oxidative deamination, ferredoxin-NADP + reductase involved in the last stage of electron transfer chain in photosynthesis, acyl-CoA dehydrogenases facilitating metabolism of fatty acids in mitochondria by catalyzing β-oxidation of fatty acids using an FAD cofactor, and many others. Flavin is also involved in the nitrogen fixation process .…”