Environmental Chemistry Letters

, Volume 15, Issue 3, pp 495–500 | Cite as

Molecular dynamics of stability and structures in phytochelatin complexes with Zn, Cu, Fe, Mg, and Ca: Implications for metal detoxification

Original Paper

Abstract

Phytochelatins, or (γ-glutamyl-cysteine)n-glycine, are specialized peptides produced by plants and algae to mitigate toxic metal exposure, for instance in response to high levels of metals such as Cu, Cd, and Zn. Stability constants and structural characterization of metal–phytochelatin complexes are lacking. This information is required to gain mechanistic insights on the metal selectivity of phytochelatins. Here, we studied structural coordination and thermodynamic stability by performing molecular dynamics simulations of a fully hydrated phytochelatin molecule complexed with Ca2+, Mg2+, Fe2+, Zn2+, and Cu2+. Our results predict the following decreasing order for the thermodynamic stability of the phytochelatin complexes: Zn2+ ≥ Cu2+ ≥ Fe2+ > Mg2+ > Ca2+. The favorable binding energies with Zn2+ and Cu2+ over the other metal cations can be explained by shorter binding distances and greater coordination from carboxylate and keto O atoms. Conformational rearrangement of phytochelatin following metal chelation was captured by monitoring changes in the solvent-accessible volume. Accessibility of solvent molecules to the phytochelatin structure was inversely proportional to the distance between the coordinated ligands and the chelated metal. These new findings demonstrate the influence of the metal–phytochelatin structure on the metal-binding thermodynamics and the phytochelatin conformation, both of which are important to evaluate the intracellular role of phytochelatin in mediating algal response to toxic heavy metal exposure.

Keywords

Phytochelatin Heavy metal Metal toxicity Metal binding 

Notes

Acknowledgements

We thank Thalia Aoki and David Flannelly for technical assistance and Beth Ahner for insightful discussions during the early stages of this work. A.L.P. acknowledges a Cornell University Graduate School Fellowship.

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Copyright information

© Springer International Publishing Switzerland 2017

Authors and Affiliations

  1. 1.The Institute for Comparative and Environmental Toxicology, Cornell UniversityIthacaUSA
  2. 2.Department of Biological and Environmental EngineeringCollege of Agriculture and Life Sciences, Cornell UniversityIthacaUSA

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