Influence of polyelectrolyte on DNA-RecA nucleoprotein filaments: poly-L-lysine used as a model.

RecA of Escherichia coli and its active nucleoprotein filaments with DNA are important for the genomic integrity and the genetic diversity. The formation of the DNA-RecA nucleoprotein filaments is a complex multiple-step process and can be affected by many factors. In this work, the effects of poly-L-lysine (PLL) on the DNA-RecA nucleoprotein filaments are investigated in vitro by agarose gel electrophoresis and atomic force microscopy (AFM). The observed morphologies vary with the concentration, the length, and the addition order of PLL. These distinctions provide information for the conformation change of DNA and the binding sites of RecA protein in the formation process of nucleoprotein filaments. Besides that, the comparison displays the effect of cationic polyelectrolyte on both inhibition and destabilization of the DNA-RecA nucleoprotein filaments. The current study provides valuable insights for pharmacologic studies and gene delivery.