First computational step towards the understanding of the antioxidant activity of the Phycocyanobilin:Ferredoxin Oxidoreductase in complex with biliverdin IX alpha
Résumé
Phycocyanobilin:Ferredoxin Oxidoreductase (PcyA) is a ferredoxin-dependent bilin reductase that converts biliverdin IX alpha (BV) into 3Z/3E-phycocyanobilin (3Z/3E-PCB) through a four-electron reduction mechanism. Using state-of-the-art QM and QM/QM' approaches, we found that the propensity of BV to bind PcyA is dominated by electrostatic interactions, especially related to the Arg149 and the Lys221 residues, while H-bonds are formed with His88 and Ser114. Our simulations also reveal that the antioxidant activity is dependent on the intramolecular non-covalent bond interactions. Indeed, we found that the surrounding residues increase the antioxidant character of BV by 2 eV. In addition, the BV antireductant capacity was investigated for the first time demonstrating that it is much more sensitive to the surrounding residues than its antioxidant counterpart. (C) 2015 Elsevier B.V. All rights reserved.