Title
Characterization of Cu(II)-reconstituted ACC Oxidase using experimental and theoretical approaches
Author
Nadia El Bakkali-Tahéri, Sybille Tachon, Maylis Orio, Sylvain Bertaina, Marlène Martinho, Viviane Robert, Marius Réglier, Thierry Tron, Pierre Dorlet, A. Jalila Simaan
Year
2017
Journal
Archives of Biochemistry and Biophysics
Abstract
1-Aminocyclopropane-1-carboxylic acid oxidase (ACCO) is a non heme iron(II) containing enzyme that catalyzes the final step of the ethylene biosynthesis in plants. The iron(II) ion is bound in a facial triad composed of two histidines and one aspartate (H177, D179 and H234). Several active site variants were generated to provide alternate binding motifs and the enzymes were reconstituted with copper(II). Continuous wave (cw) and pulsed Electron Paramagnetic Resonance (EPR) spectroscopies as well as Density Functional Theory (DFT) calculations were performed and models for the copper(II) binding sites were deduced. In all investigated enzymes, the copper ion is equatorially coordinated by the two histidine residues (H177 and H234) and probably two water molecules. The copper-containing enzymes are inactive, even when hydrogen peroxide is used in peroxide shunt approach. EPR experiments and DFT calculations were undertaken to investigate substrate's (ACC) binding on the copper ion and the results were used to rationalize the lack of copper-mediated activity.
Instrument
J-815
Keywords
Circular dichroism, Secondary structure, Ligand binding, Biochemistry