Binding of hen egg white lysozyme fibrils with nucleic acids

• HEWL fibrils bind nonspecifically with both DNA and RNA.
• Fibrils binding with RNA result in unavailability of RNA for degradation by RNase A.
• Fibril binding causes alteration in the conformation of DNA.
• Binding results in an alteration in the backbone and secondary structure of the protein.
• Structural diversity of the fibrils plays a crucial role in the interaction.

Non proteinaceous substances are found to be associated with toxic protein aggregates commonly known as fibrils. Hen egg white lysozyme (HEWL) is able to form fibrillar species under various conditions. Here for the first time we report concentration dependent binding affinities of preformed HEWL fibrils towards DNA and RNA at physiological pH (pH 7.4). We have found that HEWL fibrils bind with DNA and RNA that is distinctly different when compared to native HEWL. The association constant (Ka) of native HEWL and ct-DNA at pH 7.4 is 6.8 × 105 M−1. We have also investigated the conformational alterations of DNA that occur on binding with HEWL fibrils. Our study has demonstrated dominant electrostatic interactions between oppositely charged polyelectrolytes which accounts for the binding of nucleic acids with fibrils. The affinity between the moieties could lead to disruption in the functions of cellular components that might be attributed to the toxicity of the aggregates formed in vivo.

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