Effect of Disulfide Bonds in Antifungal Peptide from Petunia Hybrida: A Molecular Dynamics Study

The solution structure of a novel plant defensin (PhD1) contains a fifth disulfide bond, unlike other plant defensins, which have four disulfide bonds. The present study aims to better understand the stability, thermal dependence and the role of disulfide bonds in the tertiary structure of PhD1 using Molecular Dynamics (MD) simulations. The secondary structures are intact in the native structure simulated at 300 K. However, in the mutant structures a small variation is observed. A significant shift in the peptide conformation is observed when the additional fifth disulfide bond (Cys7-Cys23) is mutated. No large change in the tertiary structure conformation is observed till 400 K, which demonstrates the high thermal stability of the protein. Here, we also show that the mutation of disulfide bonds did not result in a drastic conformational change. The antifungal property along with high structural stability of the plant defensin protein makes it a promising candidate for the development of novel fungicides.