Fumarate as a key regulator of C4 organic acids metabolism in C3 plant species: novel structural insights into the allosteric site of Arabidopsis NADP-ME2

ALVAREZ, C. E.; ARIAS, C. L.; DA FONSECA REZENDE E MELLO, J.; CIRAUQI, N.; DRINCOVICH, M. F.; MENDONÇA TELES DE SOUZA, A.; GERRARD WHEELER, M. C.

Evento virtual

Congreso; Plant Biology Worldwide Summit; 2020

American Society of Plant Biologists

Arabidopsis thaliana is a C3 plant model species that accumulates high levels of C4 organic acids and uses them as transportable carbon, energy reserve and reducing power source. NADP-ME2 is a cytosolic malic enzyme present in all vegetative and reproductive organs, providing the highest malate oxidative decarboxylation activity within the gene family. Recombinant NADP-ME2 exhibits a specific and complex regulation by fumarate depending on pH and substrate/effector concentrations. Here, we investigated the fumarate binding to a allosteric site, which leads to strong enzyme activation. We proposed that this site may also bind other C4 acids including the malate substrate itself. Besides, we demonstrated the importance of residues adjacent, including the non-conserved Leu62 residue, in the transmission of the allosteric signal to the active sites inside NADP-ME2. In this regard, NADP-ME2L62W was expressed and characterized, and as predicted by molecular docking, this mutant protein is no longer regulated by fumarate and malate. This regulatory mechanism could occur in planta by varying the cellular conditions and would be relevant as NADP-ME2 controls the level of organic acids, reduced cofactors and CO2 in important processes including plant homeostasis, protein and lipid biosynthesis, sugar metabolism, and defense responses.