Molecular dynamics simulation of complexation between plasmid DNA and cationic peptides

Abstract

The elucidation of the process by which cationic peptides condense plasmid DNA (pDNA) is important for unraveling the mechanism of peptide/pDNA complex formation, which plays a vital role in gene delivery for the genetic transformation of living cells. We performed atomic MD simulations of the complexation of pDNA in the presence of two cationic peptides, KH9 (with an alternating sequence of lysine and histidine) and Cytcox (functioning as a mitochondria-targeting signal), to investigate the mechanism of pDNA condensation. The simulations revealed that the cationic peptides bound to the pDNA and that defects in pDNA formed in response to the densely packed cationic peptides, presumably initiating the folding of the double-stranded pDNA into a globule morphology. The decrease in the radius of gyration and the number of hydrogen bonds and the increase in the writhe structure, with a slightly higher tendency for the Cytcox/pDNA system, strongly support the formation of pDNA defects leading to the bending of the double helix. The results provided insight into the mechanism of pDNA complexation with cationic peptides, which should contribute to the future design of highly efficient gene delivery systems using peptide-mediated nanocarriers.