Structural and dynamical characterization of the pH-dependence of the pectin methylesterase-pectin methylesterase inhibitor complex.

Fabien Sénéchal, Olivier Habrylo, Ludivine Hocq, Jean-Marc Domon, Paulo Marcelo, Valérie Lefebvre, Jérôme Pelloux, Davide Mercadante

The Journal of biological chemistry 2017 Dec 29

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Pectin methylesterases (PMEs) catalyze the demethylesterification of pectin, one of the main polysaccharides in the plant cell wall, and are of critical importance in plant development. PME activity generates highly negatively charged pectin and mutates the physiochemical properties of the plant cell wall such that remodeling of the plant cell can occur. PMEs are therefore tightly regulated by proteinaceous inhibitors (PMEIs), some of which become active upon changes in cellular pH. Nevertheless, a detailed picture of how this pH-dependent inhibition of PME occurs at the molecular level is missing. Herein, using an interdisciplinary approach that included homology modeling, MD simulations, and biophysical and biochemical characterizations, we investigated the molecular basis of PME3 inhibition by PMEI7 in Arabidopsis thaliana Our complementary approach uncovered how changes in the protonation of amino acids at the complex interface shift the network of interacting residues between intermolecular and intramolecular. These shifts ultimately regulate the stability of the PME3-PMEI7 complex and the inhibition of the PME as a function of the pH. These findings suggest a general model of how pH-dependent proteinaceous inhibitors function. Moreover, they enhance our understanding of how PMEs may be regulated by pH and provide new insights into how this regulation may control the physical properties and structure of the plant cell wall. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Citation

Fabien Sénéchal, Olivier Habrylo, Ludivine Hocq, Jean-Marc Domon, Paulo Marcelo, Valérie Lefebvre, Jérôme Pelloux, Davide Mercadante. Structural and dynamical characterization of the pH-dependence of the pectin methylesterase-pectin methylesterase inhibitor complex. The Journal of biological chemistry. 2017 Dec 29;292(52):21538-21547